Advisor: Dr. Abraham Assefa Prepared By: Habtamu Sisay

ADDIS ABABA UNIVERSITY

ADDIS ABABA INSTITUTE OF TECHNOLOGY

SCHOOL OF GRADUATE STUDIES

SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING

Study on Quality of Site Concrete Production and its ManagementPractice in Addis Ababa Housing Projects

(Case study on Koye Feche housing Projects)

A thesis submitted to

The school of graduate studies of Addis Ababa University in partial

fulfillment of the requirement for the degree of Master of Science in

Construction Technology and Management

Advisor: Dr. Abraham Assefa

Prepared By: Habtamu Sisay

March, 2017













March, 2017













March, 2017

Study on quality of site concrete production and its management practice in Addis Ababa Housing Projects

Addis Ababa University, AAiT Page ii

AbstractConcrete, because of its versatility in use, is a major component of most of our infrastructural

facilities today. The quality of concrete is affected by its constituent materials, the equipment

used and the workmanship in concrete production process. A better or poor concrete may be

made of exactly the same ingredients based on the quality control practice of the production

process.

The city administration of Addis Ababa is building and administering condominium buildings

around the city for more than one million house seekers around different project location of

Addis Ababa. Most parts of these projects are reinforced concrete structure in which concrete

takes the major proportion among the consumed construction materials.

This research is carried out on the quality of concrete produced and the quality management

practice to enhance concrete quality under projects administered by Addis Ababa housing project

office, by taking the Koye Feche site as a case study. The research used literature review, desk

study, interview with experts and analysis of compressive strength test results on samples

collected from ongoing concrete production sites.

Statistical quality control based on compressive strength tests conducted on selected projects

reveals that, 40.4% of the test results were found to be defective based on EBCS-2:1995

compliance criteria’s. According to ACI-214 classification, 35.4% of test result based on

standard deviation indicates poor quality control whereas 71.25% of the test results show poor

quality control practice based on their coefficient of variations.

The investigation shows that, the use of poor gradation aggregate and high silt, clay, and dust

content of sand, water with impurities, problems with batching which usually called under

batching and over batching are major causes of quality problems. Furthermore, lack of attentive

control on each production process, lack of management commitment and poor workmanship in

quality concrete production is also the most frequent problems identified by respondents.

Key Words: AAHDPO, Coefficient of Variation, CQMP, Management Commitment, Quality

Control, Standard Deviation, Statistical Quality Control, TQM and Workmanship.


Addis Ababa University, AAiT Page iii

AcknowledgementFirst of all, i would like to thank God for helping me in the accomplishment of this thesis. Then,

Dr. Abraham Assefa: Thank you for your assistance. He has been there all the way for me. I also

recognize that, without him this work is very difficult to complete. Thank you Dr. Abraham!

Further thanks go to all teachers in Msc Program and special thanks for staffs of AAiT

laboratories for their valuable assistance while i collect sample specimens and testing in

laboratories. I also thank all stakeholders in Addis Ababa Housing for their cooperation while i

collect relevant data from respective sites.

Finally I would like to thank my family and friends. You were helping me in one way or another

so thank you all.


Addis Ababa University, AAiT Page iv

Table of Contents

Abstract ......................................................................................................................................................... ii

Acknowledgement ....................................................................................................................................... iii

List of Figures .............................................................................................................................................. ix

Acronyms ...................................................................................................................................................... x

CHAPTER ONE ............................................................................................................................................ i

INTRODUCTION ......................................................................................................................................... i

1.1 Statement of the Research Problem ....................................................................................................... iii

1.2 Objectives of the Research..................................................................................................................... iv

CHAPTER TWO ......................................................................................................................................... iv

LITERATURE REVIEW ............................................................................................................................ iv

2.1 Quality of concrete.................................................................................................................................. v

2.2 Concrete Materials ................................................................................................................................. vi

2.3.1 Portland Cement ................................................................................................................................ vii

2.3.1.1 Chemical Composition of Portland cement .................................................................................... vii

2.3.1.2 Hydration of Cement ...................................................................................................................... viii

2.3.1.3 Heat of Hydration ............................................................................................................................ ix

2.3.1.4 Ordinary Portland (OPC) and Portland Pozzolana Cement (PPC)................................................ ix

2.3.1.5 Storage of Cement ............................................................................................................................. x

2.3.2 Aggregates .......................................................................................................................................... xi

2.3.2.1 Physical properties of Aggregates ................................................................................................... xi

2.3.2.2 Deleterious substances in Aggregates ............................................................................................xiv

2.3.2.3 Soundness of Aggregate .................................................................................................................. xv

2.3.2.4 Alkalis and Aggregates reaction ..................................................................................................... xv

2.3.2.5 Grading of Aggregates....................................................................................................................xvi

2.3.2.6 Strength of aggregates ...................................................................................................................xvii

2.3.2.7 Handling of Aggregates .................................................................................................................xvii

2.3.3 Water for Concrete...........................................................................................................................xviii

2.3.3.1 Quality of Water for production of Concrete (Mixing Water) ......................................................xviii

2.3.3.2 Effect of Water Impurities on Properties of Concrete ....................................................................xix

2.3.3.3 Water for Curing of Concrete ..........................................................................................................xx

2.3.4 Admixtures.........................................................................................................................................xxi


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2.4 Fresh Concrete ......................................................................................................................................xxi

2.5 Production of Concrete ........................................................................................................................xxii

2.5.1Specifying Concrete ...........................................................................................................................xxii

2.5.2 Concrete Production Process ...........................................................................................................xxii

2.5.2.1 Batching ........................................................................................................................................xxiii

2.5.2.2 Mixing ...........................................................................................................................................xxiv

2.5.2.3 Transporting and placing of Concrete...........................................................................................xxv

2.5.2.4 Compaction of Concrete ..............................................................................................................xxvii

2.5.2.5 Finishing of Concrete.................................................................................................................. xxviii

2.5.2.6 Concrete Curing............................................................................................................................xxix

2.6 Concrete Quality Management ............................................................................................................xxx

2.6.1 Definition of Quality .........................................................................................................................xxx

2.6.2 Quality Management........................................................................................................................xxxi

2.6.2.1 Quality Planning .......................................................................................................................... xxxii

2.6.2.2 Quality Assurance (QA) .............................................................................................................. xxxiv

2.6.2.3 Quality Control (QC) .................................................................................................................. xxxiv

2.6.2.4 Statistical Quality Control of Concrete ...................................................................................... xxxvi

2.6.2.5 Standard Control and Compliance Criteria’s for Concrete ..................................................... xxxviii

2.7 Concrete Production Practice in Ethiopia ............................................................................................. xli

CHAPTER THREE ...................................................................................................................................xliii

RESEARCH METHODOLOGY...............................................................................................................xliii

3.1 Introduction..........................................................................................................................................xliii

3.2 Research strategy and type...................................................................................................................xliii

3.3 Study design.........................................................................................................................................xliii

3.4 Data collection methods and procedures .............................................................................................xliv

3.5 Sample size determination and sampling technique .............................................................................xlv

3.6 Ethical clearance ...................................................................................................................................xlv

CHAPTER FOUR......................................................................................................................................xlvi

CONCRETE QUALITY MANAGEMENT PLAN FOR AAHDPO PROJECTS ....................................xlvi

4.1 Introduction..........................................................................................................................................xlvi

4.2 Organization of Concrete Quality Management Plan .........................................................................xlvii

4.2.1. Introduction.....................................................................................................................................xlvii

4.2.2. Project Quality Control Organization ............................................................................................xlvii


Addis Ababa University, AAiT Page vi

4.2.3. Submittals........................................................................................................................................xlvii

4.2.4. Performance Monitoring Requirements.........................................................................................xlviii

4.2.5. Inspection and Verification Activities ............................................................................................xlviii

4.2.6. Construction Deficiencies ..............................................................................................................xlviii

4.2.7. Documentation .............................................................................................................................xlviii

4.2.8. Field Revisions.................................................................................................................................xlix

CHAPTER FIVE ........................................................................................................................................... l

FINDINGS AND DISCUSSIONS................................................................................................................. l

5.1 Introduction.............................................................................................................................................. l

5.2 Project Description................................................................................................................................. l

5.2.1 The Project............................................................................................................................................ l

5.2.2 Description of main project participants ............................................................................................. li

5.2.2.1 AAHDPO......................................................................................................................................... li

5.2.2.2 Consultants ....................................................................................................................................... li

5.2.2.3 Contractors ...................................................................................................................................... lii

5.3 Personal background of respondents...................................................................................................... lii

5.4 Statistical Quality Control of Concrete ................................................................................................. liii

5.5 Comparison between Project A and Project B ......................................................................................lxv

5.6 Quality Concrete Production Practices .............................................................................................lxvii

5.6.1 Quality of Concrete making materials .............................................................................................lxvii

5.6.1.1 Portland Cement ..........................................................................................................................lxviii

5.6.1.2 Aggregates ......................................................................................................................................lxx

5.6.1.3 Water used for Concrete Production ...........................................................................................lxxiii

5.6.2. Concrete Production ...................................................................................................................... lxxiv

5.6.2.1 Batching of Concrete ....................................................................................................................lxxv

5.6.2.2 Mixing of concrete ..................................................................................................................... lxxviii

5.6.2.3 Transporting and Placing of Concrete ........................................................................................ lxxix

5.6.2.4 Compaction of Concrete ............................................................................................................... lxxx

5.6.2.5 Curing of Concrete ...................................................................................................................... lxxxi

5.7 Concrete Quality Management of AAHDPO ................................................................................... lxxxii

5.7.1 Management Commitment ............................................................................................................ lxxxiii

5.7.2 Companies and Personnel Qualification ...................................................................................... lxxxiv

5.7.3. Manpower and Workmanship ...................................................................................................... lxxxvi


Addis Ababa University, AAiT Page vii

CHAPTER SIX ..................................................................................................................................... lxxxvii

CONCLUSIONS AND RECOMMENDATIONS ............................................................................... lxxxvii

6.1 Conclusions.................................................................................................................................... lxxxviii

6.2 Recommendations............................................................................................................................ lxxxix

References....................................................................................................................................................xc


Addis Ababa University, AAiT Page viii

List of Tables

Table 2.1 Approximate oxide composition of ordinary Portland cement...............................9

Table 2.2 limits of permissible impurities in water ..............................................................21

Table 2.3 Recommended Concrete Mixing Times ...............................................................27

Table 2.4 Principal sources of strength variations in concrete production and quality

testing.....................................................................................................................38

Table 2.5 Standard deviation for different control standards................................................41

Table 2.6 Coefficient of variation for different control standards.........................................41

Table 2.7 Margins of Strength in MPa,..................................................................................42

Table 5.1 Compressive Strength test results and analysis, according to EBCS-2 1995 and

ACI-318 of Project A.............................................................................................57

Table 5.1.a Summary of compliance and conformity from table 5.1.......................................60

Table 5.2.a Level of control based on Standard Deviation (ACI-214).....................................60

Table 5.2.b Level of control based on Coefficient of variation (ACI-214)..............................61

Table 5.3 Compressive Strength test results and analysis, according to EBCS-2 1995 and

ACI-318 of Project B.............................................................................................63

Table 5.3.a Summary of compliance and conformity from table 5.3.......................................66

Table 5.4.a Level of control based on Standard Deviation (ACI-214).....................................67

Table 5.4.b Level of control based on coefficient of variation (ACI-214)...............................67

Table 5.5 Implementation of QMS in AAHDPO Projects....................................................87

Table 5.6 Management Commitment to improve concrete production in AAHDPO

Projects...................................................................................................................88

Table 5.7 Adequacy of companies and personnel to enhance concrete quality of

AAHDPO projects.................................................................................................89


Addis Ababa University, AAiT Page ix

List of FiguresFigure 2.1 Balanced Cost of Quality chart...............................................................................35

Figure 2.2 Normal frequency curves for three different distributions with the same mean

but different variability..........................................................................................39

Figure 5.1 Control of concrete production of Project A using Shewart chart method............62

Figure 5.2 Control of concrete production of Project B using Shewart chart method............68

Figure5.3 Dumped fine aggregate (Sand) for concrete production with much silt

and dusts................................................................................................................75

Figure 5.4 Coarse aggregates for concrete with poor gradation..............................................76

Figure 5.5 Water tankers with impurities from the surrounding sites.....................................78

Figure 5.6 Common problems of batching..............................................................................81

Figure 5.7 Common Concrete columns Placing Practices in AAHDPO Projects...................84


Addis Ababa University, AAiT Page x

Acronyms

AAHDPO-----Addis Ababa Housing Project Office

ACI-------------American Concrete Institute

ASR-------------Alkali Silica Reaction

EBCS-----------Ethiopian Building code of Standards

ES---------------Ethiopian Standards

ESA ------------Ethiopian Standards Agency

QMP------------Quality Management Plan

QMS------------Quality Management System

QC--------------Quality Control

QA--------------Quality Assurance

CQMP----------Concrete Quality Management Plan

SQC-------------Statistical Quality Control

GDP------------Gross Domestic Product

GTP-------------Growth and Transformation Plan

MSEs-----------Micro and Small Scale Enterprises

CHAPTER ONE

INTRODUCTION

Concrete, because of its versatility in use, is a major component of most of our infrastructural

facilities today. It is the most widely used construction material in the world, and its popularity

can be attributed to two aspects. First, concrete is used for many different structures, such as

building frames, dams, pavements, building or bridges. Second, the amount of concrete used is

much more than any other material in the world [1].

Concrete is produced from three basic materials namely water, cement, aggregates (fine and

course aggregates) and sometimes an admixture may also be used in a certain prescribed

proportion to improve some properties of concrete. The quality of the concrete is affected by its

constituent materials, the equipment used and the workmanship in concrete production process.

Concrete production process includes: batching, mixing, transporting and placing, compacting

finishing of unformed concrete surfaces, and curing of concrete. A better or poor concrete may

be made of exactly the same ingredients if there is a difference on the quality control of the

production process. Hence, quality control mechanisms for concrete should be in use. Quality

control in concrete production is a means of checking concrete ingredients and production

processes are in compliance with the requirements stated in the specification or code of practices.

In order to have a good quality of concrete it should be done as per the specification given by the

designer to address the desired design objectives.

Given that the materials and proportions of ingredients are suitable and properly selected, the

quality of concrete depends on the knowledge of the person(s) responsible for the concreting

operations. If these people have insufficient knowledge and experience, they are likely to be

unaware of the concreting problems which may seriously affect the quality. Thus, the quality of

the concrete produced will be poor and may not meet the requirements of the specifications.

Concrete structures are designed and constructed so that they maintain their required

serviceability, durability and performance for a sufficiently long period of time, which is

expected to be in excess of 50 years. Concrete structures fail when it can no longer provide the

required strength to support its designed load. The failure of concrete can sometimes be mild

with visible cracks and deflections or severe, leading to partial or total collapse of the structure

Proposed Quality Management plan for concreting works in AAHDPO Projects

Addis Ababa University, AAiTPage ii

either during the construction or post-construction stage. To obtain quality concrete products,

proper care and control has to be done during ingredient selection, checking compliance with the

standards, production processes and workmanship. Repairing poor quality concrete structure is

costly, undesirable, time consuming, and in many cases not possible. Therefore, every effort

should be made to avoid the production of a poor quality concrete structures and it should also be

reminded that all professionals and firms involved in the construction industry have to give

special emphasis to quality control.

Currently, Ethiopia is registering high growth rate and construction is go through with a lot of

capital investment. In major cities and towns, buildings and infrastructure construction projects

are highly observed. Most of these projects are reinforced concrete structures in which concrete

takes the major proportion among the consumed construction materials. This is an indication as

how much the quality of concrete is important for the overall quality of a building, as the major

components of a building are made with concrete such as foundations, columns, beams and slabs

which are load bearing elements.

The housing challenge in Ethiopia is very high. According to a UN Habitat report in 2011, the

housing deficit was between 900,000 and 1,000,000 units in urban areas, and only 30 percent of

the current housing stock is in fair condition, with the remaining 70 percent in need of total

replacement. According to the report, in Addis Ababa alone, 300,000 housing units are required

to meet the deficit. Therefore, the government has been building condominium houses as part of

its integrated housing development program and Addis Ababa has received priority due to the

high demand for housing. Even though UN report says 300,000 housing unit meets the deficit,

close to one million individuals that seek condos have been registered since 2012 in Addis

Ababa only, according to the Ministry of Urban Works and Development. In the last few years,

the city administration has completed thousands of condos in the central part of town, although

most of the high raised condominium compounds have been built on the outskirts of Addis

Ababa.

According to the Grand Transformation Plan II (GTP II), the government plans to construct 430

thousand housing units in all schemes and 63 thousand in partnership with private companies.

The plan also intends to earmark 86 billion birr for domestic expenses and USD 1.4 billion in

foreign currency and a further USD 1.3 billion to be made available for foreign real estate


Addis Ababa University, AAiTPage iii

companies. This plan seems overstated and it is difficult to allocate such amount of money for

those projects with the current country’s situation. In addition to this, there is no available

condominium project under construction in partnership with private companies and foreign real

estate companies.

Concrete is a major construction material commonly and regularly used on those buildings. Any

type of reinforced concrete framed building construction work constitute at least about 40% of

the total works is concrete work [4]. Given that concrete is usually non-factory product or cast in

situ product, especially in Ethiopia where it is mostly produced on site manually, it is very

important and proper to study its quality and utilization.

Hence, the fact that concrete forms the load bearing parts of a building and the variability in

concrete product became leading motivational factors to undertake research on the public

buildings so that to identify the problems associated with the quality of site concrete production

practices in Addis Ababa Housing projects and at the end to suggest ways of improving it.

1.1 Statement of the Research ProblemDue to high deficit of Housing in Addis Ababa, the government of Ethiopia and the city

administration is involved in an integrated housing development program which is government

led and financed housing program. The Government built and transfer more than 171,000

housing units for house seekers and still the demand is far from being fulfilled. In Addis Ababa

only, more than 900,000 peoples are registered to have a condominium house and the

government also planned and to earmark 86 billion birr for domestic expenses and USD 1.4

billion in foreign currency to be made available for foreign real estate companies in the second

GTP. Even though all this much budget is allocated to build residential condominium houses,

most of stakeholders have worry on the quality of those buildings which are completed and

under construction. Fear to the collapse of condominium house at Gerji condominium site,

demolished and reconstructed concrete structures at Gelan site, minor and major cracks observed

on many condominiums could be good examples. Since these buildings are usually made of

concrete structures which cost a significant amount out of the total cost of the project, the

concrete should only become a quality material for the construction. Though there is no a

research done on the quality of concrete used on those buildings that has been done till now,

different stakeholders believe that the concrete they use is low quality due to impurities in sand,


Addis Ababa University, AAiTPage iv

uncontrolled concrete production process and poor workmanship. This creates fears to the

quality of this project among stakeholders. The researcher also participated on the construction

of these housing projects and observed many problems in concrete production that hinder the

quality of concrete. Hence, this research tries to investigate current concrete production, quality

of the concrete produced and quality management practices in Addis Ababa housing projects.

1.2 Objectives of the ResearchThe objectives of this research are stated as follows:

Investigate the quality of site concrete production in Addis Ababa Housing projects

Investigate concrete quality management practices on those projects

Examine the quality of concrete produced by considering their compressive strength via

taking sample specimens from ongoing projects from selected sample sites at Koye Feche

housing project.

Finally the research will set conclusion that it reaches and recommendations regarding to the

quality of site concrete production and management practices in Addis Ababa Housing Projects.

CHAPTER TWO

LITERATURE REVIEW

This chapter focuses on general review of literature and concepts available on quality of concrete

production process and findings from different researchers who have been published on different


Addis Ababa University, AAiTPage v

journals and books. The chapter will extensively review the quality concept of concrete, concrete

making materials, physical and chemical properties of those materials, the production process

and the workmanship that primarily determine the overall concrete quality. It further deals and

review available literatures and researches which relates with concepts of quality management

principles and its application in concrete production.

2.1 Quality of concrete

Quality is defined as the totality of features and characteristics of a product for service that bears

on its ability to satisfy the projects functional requirements. The quality of output is always

agreed upon between the supplier and the client (in case of construction project works, usually

the contractor and the employer, represent the supplier and client, respectively), and the quality

objective is to achieve zero defects with best quality of the project works. This is possible only

by ensuring quality control at every stage of the construction process. Quality is conformity to

standards and requirements to achieve excellence [7].

Quality concrete is that which is capable of meeting the requirements of the job in terms of

strength, durability and appearance. Strength is often the major feature in defining the quality

because strength is both easy to define and to measure. Therefore in many cases, strength is the

unique measurement of concrete quality [9].

A quality concrete is that one who fits to its purpose. This means the product must meet or

exceed the customer requirements and this needs improvement of concrete production. Quality

improvement refers to product improvement, process improvement and people based

improvement. Process improvement relates to a series of action directed towards a specific aim

of quality production of concrete. People based improvement refers to the employment of

personnel with adequate skill, knowledge and experience needed for accuracy and performance

improvement of in-situ concrete [7,13].

Concrete is a variable material, and to meet the requirements described or its intended quality, its

production, handling, compaction, finishing, and curing procedures must be controlled, as well

as its ingredients. Quality of concrete can only be obtained by skilled supervisors and well

trained workers who understand the science of concrete. Hence, the workmanship of concreting

operations is therefore supreme in maintaining the required concrete quality. The specifications

should also contain sufficient information on the workmanship requirements as well as on


Addis Ababa University, AAiTPage vi

materials to maintain satisfactory supervision. A good level of supervision helps to improve the

standard of workmanship on the site [16].

Hence, it is the aim of this chapter of the research to briefly discuss about the ingredients of

concrete and its production processes in depth by referring different literatures written on this

area around the world. Quality management of concrete will also be briefly discussed.

2.2 Concrete MaterialsConcrete is a composite material which consists a binding medium within which are embedded

particles or fragments of relatively inert mineral fillers. In concrete, the binder matrix is a

combination of cement and water; it is commonly called the "cement paste and the filler

material, called "aggregate," is generally graded in size from fine sand to pebbles or fragments of

stone [3].The paste is composed of cementitious materials, water, and entrapped air or purposely

entrained air. It constitutes about 25% to 40% of the total volume of concrete. Different

literatures show that, the absolute volume of cement is usually between 7% -15% and the water

between 14% - 21%. Air content in air-entrained concrete ranges from about 4% to 8% of the

total volume. Aggregates make up about 60% to 75% of the total volume of concrete, their

selection is important in concrete quality [2, 6, 8].

Aggregate-coarse and fine combined occupy about 70% space in a given mass of concrete and

the rest 30% space is filled by water, cement and air voids [11]. The same literature asserted that,

the proportions of each of concrete materials control the strength and quality of the resultant

concrete. Green concrete is a plastic mass, which can be molded into any desired shape. This is

its main advantage as a construction material.

2.3 Regular Concrete

Regular concrete is a term describing concrete that is produced by using cement, sand and coarse

aggregate, with or without use of chemical admixtures. Mix proportions are selected as specified

for nominal mix of desired characteristic strength or as determined by following a Design Mix

approach. This concrete can be produced to yield desired strength of about 10 MPa to over 50

MPa, depending on the purpose, ranging from plain concrete to structural concrete [3].

Concrete, when it is fresh, should be workable and at the same time be cohesive. Good

workability is required to place and compact the fresh concrete and cohesiveness is required to


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avoid segregation while transporting, placing and compacting. In the hardened state, concrete

should be strong, durable and should have minimum voids. It must have sufficient strength,

resistant to abrasion, impermeability to resist weathering, chemical attack and corrosion [3,6].

Since regular concrete is very common that is produced in Ethiopia frequently, this thesis is

limited to the description of ingredients that produce regular concrete.

2.3.1 Portland CementCement is a material with adhesive and cohesive properties which make it capable of bonding

minerals fragments into a hard continuous compact mass. The name "Portland cement" is given

originally due to the resemblance of the color and quality of the hardened cement to Portland

stone – Portland Island in England [3].

The raw materials required for manufacture of Portland cement are calcareous materials, such as

limestone or chalk, and argillaceous material such as shale or clay. Portland cement is the most

common type of cement which is produced in all cement factories in Ethiopia.

The process of manufacture of cement consists of grinding the raw materials, mixing them

intimately in certain proportions depending upon their purity and composition and burning them

in a kiln at a temperature of about 1300 to 1500°C, at which temperature, the material sinters and

partially fuses to form nodular shaped clinker. The clinker is cooled and ground to fine powder

with addition of about 3 to 5% of gypsum. The product formed by using this procedure is

Portland cement.

There are two processes known as “wet” and “dry” processes depending upon whether the

mixing and grinding of raw materials is done in wet or dry conditions. With a little change in the

above process we have the semi-dry process also where the raw materials are ground dry and

then mixed with about 10-14 percent of water and further burnt to clinkering temperature. The

dry process requires much less fuel as the materials are already in a dry state, whereas in the wet

process the slurry contains about 35 to 50 percent water. To dry the slurry we thus require more

fuel. In Ethiopia most cement factories use dry process to produce Portland cement [1,2,6].

2.3.1.1 Chemical Composition of Portland cementThe raw materials used for the manufacture of cement consist mainly of lime, silica, alumina and

iron oxide. These oxides interact with one another in the kiln at high temperature to form more

complex compounds. These compounds are tricalcium silicate (C3S), dicalcium silicate (C2S),


Addis Ababa University, AAiTPage viii

tricalcium aluminate (C3A) and tetra calciumaluminoferite or iron compound (C4AF) which are

usually regarded as the major constituents of cement. The relative proportions of these oxide

compositions are responsible for influencing the various properties of cement; in addition to rate

of cooling and fineness of grinding [1,6].

Table 2-1 Approximate oxide composition of ordinary Portland cement. Source: [1, pp 14]

Oxide Composition Percent Content

CaO 60–67

SiO2 17–25

Al2O3 3.0–8.0

Fe2O3 0.5–6.0

MgO 0.1–4.0

Alkalies (K2O, Na2O) 0.4–1.3

SO3 1.3–3.0

2.3.1.2 Hydration of CementHydration is the reaction (series of chemical reactions) of cement with water to form the binding

material. In other words, in the presence of water, the silicates (C3S and C2S) and aluminates

(C3A and C4AF) form products of hydration which in time produce a firm and hard mass – the

hydrated cement paste [2].

The hydration process is not an instantaneous one. It is fast during the first few minutes of

mixing and decreases continuously with time. Because of reduction in rate of hydration even

after a long time there remains an appreciated amount of unhydrated cement. For this reason,

there is hydration at any time after hardening of concrete though it is at a very lower rate [2,4,6].

The various compounds of cements mentioned previously has different rate of hydration, the rate

of hydrations of C4AF is higher than the three major compounds of cement. C3A has higher rate

than C3S and C2S; and C3S has higher rate of hydration than C2S [3].The hydration products of

the major cement compounds, C3S and C2S, gives calcium silicate hydrates which is commonly

designated as C-S-H. This hydrate product determines the basic physical properties of concrete

such as setting and strength gain [1].


Addis Ababa University, AAiTPage ix

2.3.1.3 Heat of HydrationThe reaction of cement with water is exothermic. The reaction liberates a considerable quantity

of heat, which may reach up to 500 joules per gram (120 cal/ gram). This liberation of heat is

called heat of hydration. This is clearly seen if freshly mixed cement is put in a vacuum flask and

the temperature of the mass is read at intervals. The study and control of the heat of hydration

becomes important in the mass concrete constructions. It has been observed that the temperature

in the interior of large mass concrete is higher. Similarly, the exterior of the concrete mass loses

some heat so that a steep temperature gradient may be established, and during subsequent

cooling of the interior serious cracking may result [2].

Due to the reason that different climatic zones exist in Ethiopia, it is better to use appropriate

type of cement to an appropriate climatic zones to avoid early setting or the use of retarders on

hot areas is recommendable to improve effect of early reactions. On contrary, the heat produced

by the hydration of cement may prevent freezing of the water in the capillaries of freshly placed

concrete in cold weather, and a high evolution of heat is therefore advantageous. It is clear then,

that it is advisable to know the heat producing properties of different cements in order to choose

the most suitable cement for a given purpose or environment [2].

2.3.1.4 Ordinary Portland (OPC) and Portland Pozzolana Cement (PPC)There are many types of Portland cements that are produced around the world. These cements

are used for specific intended purpose. Among different types of cements, Ordinary and

Pozzolanic Portland cements, OPC and PPC, respectively, are common cement types which are

mostly produced by the cement factories in Ethiopia and used for concrete production. Thus, the

properties of these two cement types are discussed below.

Ordinary Portland cement is the most common cement used in general concrete construction

when there is no exposure to sulfates in the soil or in groundwater. The manufacture of OPC is

decreasing all over the world in view of the popularity of blended cement on account of lower

energy consumption, environmental pollution, economic and other technical reasons [1]. Even

though production of OPC around the world is decreasing due to blending substitutes, the

production and consumption of OPC cement in Ethiopia is very high.


Addis Ababa University, AAiTPage x

Portland Pozzolana cement (PPC) is manufactured by the intergrinding of OPC clinker with 10

to 30 percent of pozzolanic material. A pozzolanic material is essentially a silicious or aluminous

material which in itself possessing no cementitious properties, which will, in finely divided form

and in the presence of water, react with calcium hydroxide, liberated in the hydration process, at

ordinary temperature, to form compounds possessing cementitious properties. The pozzolanic

materials generally used for manufacture of PPC are calcined clay or fly ash. In Ethiopia, Pumice

which amounts from 14 to 28 percent is the most frequently used volcanic rock material for the

production of PPC in most of the cement production factories.

Portland Pozzolana Cement has considerable advantages over OPC when made by using

optimum percentage of right quality of fly ash. The advantages of PPC are mainly due to the

slow conversion of calcium hydroxide in the hydrated cement paste into cementitious product.

PPC is economical because costly clinker is replaced by cheaper pozzolanic material. It has also

durability characteristics than OPC particularly in hydraulic structures because soluble calcium

hydroxide is converted into insoluble cementitious products resulting in improvement of

permeability. PPC generates reduced heat of hydration and that too at a low rate. The long term

strength of PPC beyond a couple of months is higher than OPC if enough moisture is available

for continued pozzolanic action [1,3,4,6].

2.3.1.5 Storage of CementCement being very finely ground is highly hygroscopic i.e. they absorb moisture readily from

air. Therefore, it is essential to protect them from dampness before they are used, so that they

may fulfill their intended functions. Even when stored under good conditions bagged cement

may lose 20 percent of its strength after 2 months of storage, and 40 percent after 6 months of

storage [6]. Cement can be stored in air tight bins indefinitely without deteriorating in any way,

but this is impractical for site concrete production. Different literatures shows that, cement which

is 4 months old and above should be classified as "aged" and vital cement tests should be

rechecked for concrete production [6,13,16].

If the cement supply or stock is doubtful laboratory tests should be undertaken to be sure whether

it is suitable or no longer to use. In case of laboratory tests are unattainable pointed out that, its

purity and quality can be judged through simple field tests .On such conditions, the quality

control team or any other professional can identify cement with dilemma. According to Gupta


Addis Ababa University, AAiTPage xi

and Gupta (2004), the color of pure cement should be uniformly greenish gray, when cement

rubbed in between thumb and fore finger, it should feel smooth hence grittiness shows

adulteration. Another checking mechanism is using small quantity of cement which shall be

thrown into a bucket of water and a good quality of cement will float and it will sink if the

cement contains impurities [9].

2.3.2 AggregatesAggregates are the important constituents in concrete. They give body to the concrete, reduce

shrinkage and affect economy. Approximately three-quarters of the volume of conventional

concrete is occupied by aggregate. It is predictable that a constituent occupying such a large

percentage of the mass should contribute important properties to both the fresh and hardened

state of the product. Aggregates were considered as chemically inert materials but now it has

been recognized that some of the aggregates are chemically active and also that certain

aggregates exhibit chemical bond at the interface of aggregate and paste [1,4,6].

2.3.2.1 Physical properties of Aggregatesi. Aggregate Size, Shape and Texture

The largest maximum size of aggregate practicable to handle under a given set of conditions

should be used. Generally, the maximum size of aggregate should be as large as possible within

the limits specified, but in any case not greater than one-fourth of the minimum thickness of the

member. Using the largest possible maximum aggregate size will result in reduction of the

cement content, reduction in water requirement and reduction of drying shrinkage [4].

The aggregate shape affects the workability of concrete due to the differences in surface which

are caused by different shapes. Sufficient paste is required to coat the aggregate to provide

lubrication. It is difficult to really measure the shape of irregular body like concrete aggregate

which are derived from various rocks. Not only the characteristic of the parent rock, but also the

type of crusher used influence the shape of aggregates. Generally the most common shapes of

aggregates can be irregular, angular, rounded, flaky, etc.[4].


Addis Ababa University, AAiTPage xii

From the standpoint of economy in cement requirement for a given water/cement ratio, rounded

aggregates are preferable to angular aggregates. On the other hand, the additional cement

required for angular aggregate is offset to some extent by the higher strengths and sometimes by

greater durability as a result of the interlocking texture of the hardened concrete and higher bond

characteristic between aggregate and cement paste. Flat particles in concrete aggregates will

have particularly objectionable influence on the workability, cement requirement, strength and

durability. In general, excessively flaky aggregate makes very poor concrete [1].

Surface texture is the property, the measure of which depends upon the relative degree to which

particle surfaces are polished or dull, smooth or rough. Surface texture depends on hardness,

grain size, pore structure, structure of the rock, and the degree to which forces acting on the

particle surface have smoothed or roughened it. Hard, dense, fine-grained materials will

generally have smooth fracture surfaces. Generally it has significant influence on the fluidity of

fresh concrete and the bond between aggregate and cement paste of hardened concrete [4].

ii. Porosity and Absorption Aggregates

The porosity, permeability, and absorption of aggregates influence the resistance of concrete to

freezing and thawing, bond strength between aggregate and cement paste, resistance to abrasion

of concrete etc. The cement paste due to its viscosity cannot penetrate to a great depth into the

pores except the largest of the aggregate pores. When all the pores in the aggregate are full with

water, then the aggregate is said to be saturated and surface-dry [3,6]

The water absorption of aggregate is determined by measuring the increase in mass of an oven-

dried sample when immersed in water for 24 hours (the surface water being removed). The ratio

of the increase in mass to the mass of the dry sample, expressed as a percentage, is termed as

absorption. It may be noted that gravel has generally a higher absorption than crushed rock of the

same petrological character because weathering results in the outer layer of the gravel particles

being more porous and absorbent. Although there is no clear-cut relation between the strength of

concrete and the water absorption of aggregate used, the pores at the surface of the particle affect

the bond between the aggregate and the cement paste, and may thus exert some influence on the

strength of concrete [3,6].

iii. Moisture content of Aggregates


Addis Ababa University, AAiTPage xiii

Aggregate exposed to rain collects a considerable amount of moisture on the surface of the

particles and, except at the surface of the stockpile, keeps this moisture over long periods. This is

particularly true of fine aggregate and the surface-or free moisture (in excess of that held by

aggregate in a saturated and surface-dry condition) must be allowed for in the calculation of

batch quantities. Coarse aggregate rarely contains more than one percent of surface moisture but

fine aggregate can contain in excess of ten percent. The surface moisture is expressed as a

percentage of the mass of the saturated and surface-dry and called moisture content.

Determining of the moisture content of an aggregate is crucial in order to determine the net

water-cement ratio for a batch of concrete. If the moisture content and absorption of aggregates

is not properly determined, the water added during preparing the mix becomes variable. This

results in either high or low water to cement ratio. Therefore, there is no doubt that continuous

measurement of moisture and automatic adjustment of the amount of water added into the mixer

greatly reduce the variability of the concrete produced when the moisture content of the

aggregate is variable [3,6].

iv. Bulking of Fine Aggregates

The moisture present in fine aggregate causes increase in its volume known as bulking of sand.

The moisture in the fine aggregate develops a film of moisture around the particles of sand and

due to surface tension push, apart the sand particles, occupying greater volume. The presence of

moisture in aggregate necessitates correction of the actual mix proportions: the mass of water

added to the mix has to be decreased by the mass of the free moisture in the aggregate, and the

mass of the wet aggregate must be increased by a like amount [1,6].

The bulking of the sand affects the mix proportion if mix is designed by volume batching.

Bulking results in smaller weight of sand occupying the fixed volume of the measuring box, and

the mix becomes deficient in sand and the resulting concrete becomes honey combed and its

yield is also reduced. Volume batching therefore represents bad practice and should be

discouraged [13].


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2.3.2.2 Deleterious substances in AggregatesThe concrete aggregates should be free from impurities and deleterious substances which are

likely to interfere with the process of hydration, prevention of effective bond between the

aggregates and matrix. The impurities sometimes reduce the durability of the aggregate [1].

Fine aggregates which usually obtained from natural sources are likely to contain organic

impurities in the form of silt and clay. The manufactured fine aggregate does not normally

contain organic materials. But it may contain excess of fine crushed stone dust. Coarse aggregate

stacked in the open and unused surfaces for long time may contain moss and mud in the lower

level of the stack. Sometimes excessive silt and clay contained in the fine or coarse aggregate

may result in increased shrinkage or increased permeability in addition to poor bond

characteristics. The excessive silt and clay may also necessitate greater water requirements for

given workability [1,6].

Sand is normally dredged from river beds and streams in the dry season when the riverbed is dry

or when there is not much flow in the river. Under such situation along with the sand, decayed

vegetable matter, humus, organic matter and other impurities are likely to settle down. But if

sand is dredged when there is a good flow of water from very deep bed, the organic matters are

likely to get washed away at the time of dredging. The organic matters will interfere with the

setting action of cement and also interfere with the bond characteristics with the aggregates. The

presence of moss or algae will also result in entrainment of air in the concrete which reduces its

strength [1,6].

The quantity of clay, fine silt and fine dust are determined by sedimentation method. In this

method, a sample of aggregate is poured into a graduated measuring jar and the aggregate is

nicely rodded to dislodge particles of clay and silt adhering to the aggregate particles. The jar

with the liquid is completely shaken so that all the clay and silt particles get mixed with water

and then the whole jar is kept in an undisturbed condition. After a certain time interval, the

thickness of the layer of clay and silt standing over the fine aggregate particles will give a fair

idea of the percentage of clay and silt content in the sample of aggregate under test. According to

Ethiopian standards, the maximum limit of silt content is allowed up to 6%. Sand with silt

content greater than 6% should be washed or rejected from concrete production.


Addis Ababa University, AAiTPage xv

Fine aggregate from tidal river or from pits near sea shore will generally contain some

percentage of salt. The contamination of aggregates by salt will affect the setting properties and

ultimate strength of concrete. Salt being hygroscopic, will also cause efflorescence and unsightly

appearance. Opinions are divided on the question whether the salt contained in aggregates would

cause corrosion of reinforcement. But studies have indicated that the usual percentage of salt

generally contained in the fine aggregate will not cause corrosion in any appreciable manner.

However, it is a good practice to wash sand containing salt more than 3% [1].

2.3.2.3 Soundness of AggregateSoundness refers to the ability of aggregate to resist excessive changes in volume as a result of

changes in physical conditions. These physical conditions that affect the soundness of aggregate

are the freezing, the thawing, and variation in temperature, alternate wetting and drying under

normal conditions and wetting and drying in salt water. Aggregates which are porous, weak and

containing any undesirable extraneous matters undergo excessive volume change when subjected

to the above conditions. Aggregates which undergo more than the specified amount of volume

change are said to be unsound aggregates. If concrete is liable to be exposed to the action of

frost, the coarse and fine aggregate which are going to be used should be subjected to soundness

test [1,4,6].

The physical causes of large or permanent volume changes of aggregate are freezing and

thawing, thermal changes at temperatures above freezing and alternating wetting and drying. If

the aggregate is unsound, such changes in physical conditions result in a deterioration of the

concrete in the form of local scaling, pop-outs, and even extensive surface cracking.

Unsoundness is exhibited by porous flints and cherts, especially lightweight ones with a fine

textured pore structure, by some shales and by other particles containing clay minerals [1,4,6].

2.3.2.4 Alkalis and Aggregates reactionIt is known that aggregates should be inert material but researches shows that they are not fully

inert. Some of the aggregates contain reactive silica which reacts with the alkali (sodium oxide

Na2O and potassium oxide K2O) present in cement which termed as alkali Silica reaction (ASR).

In Ethiopia there are different potentially reactive silica minerals and rocks that may be used for

concrete production. The rocks which contain reactive constituents are siliceous limestone, trap

and certain types of sandstones. These reactive constituents may be in form of volcanic glass,

zeolites, opals, cherts, quartz etc, the gels produced during reaction swells by absorbing water


Addis Ababa University, AAiTPage xvi

[35]. As this gel is confined by the surrounding cement paste, internal pressure increases

resulting to disruption of concrete by expansion, and cracking of concrete and eventually failure

of concrete structures takes place. The rate of deterioration may be fast or slow depending upon

the conditions. It is believed that the swelling of the hard aggregate particles is most harmful to

the concrete [4].

The most important factors that promote alkali-aggregate reactions are, reactive type of

aggregate, high alkali content in cement, availability of moisture and optimum temperature

conditions. Therefore, in order to avoid or eliminate this reaction which affects the overall

quality of concrete, some control mechanisms should be provided [13]. The same study asserted

that, the alkali aggregate reaction can be controlled by the selection of non-reactive aggregates,

use of low alkali cement 0.6–0.4 alkali content cement, use of admixtures such as pozzolana,

controlling void space in concrete and by controlling moisture and temperature [13].

Another type of deleterious aggregate reaction is that between some dolomitic limestone

(carbonates) aggregates and the alkalis in cement which usually termed as alkali carbonate

reactions (ACR). It is likely that the gel which is formed is subject to swelling in a manner

similar to swelling clays. Thus, under humid conditions, expansion of concrete takes place.

Therefore, the amount and type of the mineralogical content of aggregates used in concrete

production is indispensable for determining the resulting quality of concrete [6].

2.3.2.5 Grading of AggregatesThe particle size distribution of aggregates is called grading. Grading determines the paste

requirement for a workable concrete since the amount of voids among aggregate particles

requires the same amount of cement paste to fill out in the concrete mixture. In making concrete,

aggregates must be graded such that the smaller particles of the fine aggregate fill the voids

created by the coarse aggregate. The cement paste fills the voids in the fine aggregate thus

forming a dense mix. Principle of grading is that smaller size particles fill up the voids left in

larger size particles. By adopting proper percentages, of various sized aggregates composite

aggregate mix can be developed which will be thoroughly graded to produce dense concrete

together with smaller quantities of fine aggregate and cement [2].


Addis Ababa University, AAiTPage xvii

The way particles of aggregate fit together in the mix, as influenced by the gradation, shape, and

surface texture has an important effect on the workability and finishing characteristic of fresh

concrete, consequently on the properties of hardened concrete. One of the most important factors

for producing workable concrete is good gradation of aggregates. Good grading implies that a

sample of aggregates contains all standard fractions of aggregate in required proportion such that

the sample contains minimum voids. The grading of aggregate is determined by sieve analysis.

The process of dividing a sample of aggregate into fractions of same particle size is known as

sieve analysis and its purpose is to determine the grading or size distribution of the aggregate [1].

2.3.2.6 Strength of aggregatesSince aggregates ranges from 65% to 75% of concrete volume, it contributes a significant role on

the strength possessed by concrete due to its higher modulus of elasticity as compared to the

cement paste. To have a strong concrete, the aggregate should have high load bearing capacity

and resistant to wearing and abrasion effects. To assess the strength of aggregates, a number of

strength tests are carryout in laboratories. Some of these are; aggregate crushing value, aggregate

impact value, Los Angeles abrasion test, ten percent fines values etc. Therefore, aggregates in

use for concrete production have to be strong that satisfy standards requirement.

2.3.2.7 Handling of AggregatesHandling and stockpiling of coarse aggregate can easily lead to segregation, more especially

when the aggregate has to roll down a slope. While stockpiling aggregate at site proper handling

mechanisms should be used [13]. The same study lists the following precautions for handling of

aggregates:

1. Coarse as well as the fine aggregates should be stored on a hard and dry ground. It should

never be dumped on loam or grass. If aggregate is dumped on loam or grass, dirt and

rubbish will be carried into the concrete. If hard surface is not available, a platform of

planks, or old corrugated iron sheets, or floor of brick or a thin layer of weak concrete or

so should be prepared.

2. Piles of sand and coarse aggregate, as well as piles of different sized coarse aggregate

should be kept separate by means of compartment walls. These fractions should be

remixed in the desired proportion at the time of feeding them into the mixer.

3. Care should be taken to avoid breakage of the aggregate.


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4. The bide ends, tea leaves or sugar etc. should not be allowed to be thrown into the

aggregate piles. The tobacco of bidi or nicotine of tea leaves or sugar will slow down the

setting of the concrete. Tree leaves or grass roots etc. will also damage the binding

properties of concrete. Hence, aggregate should be kept clean.

5. While stockpiling, successive consignments should not be dropped at the same place.

This will lead to segregation of aggregate.

2.3.3 Water for ConcreteWater is an important ingredient of concrete, and a properly designed concrete mixture, typically

with 15 to 25% water by volume, will possess the desired workability for fresh concrete and the

required durability and strength for hardened concrete. Since it helps to form the strength giving

cement gel, the quantity and quality of water is required to be looked into very carefully. In

practice, very often great control on properties of cement and aggregate is exercised, but the

control on the quality of water is often neglected. Since quality of water affects the strength, it is

necessary to go into the purity and quality of water [1,4].

The properties of water have been found to influence the properties of concrete to a great extent.

For concrete production water is used for preparing concrete i.e. for mixing concrete ingredient,

curing concrete and for washing aggregates. In most cases the effect of impure water on concrete

manifests gradually over time and devastating eventually whereas, in some adverse cases, the

manifestation occur immediately. To prevent such irreversible negative effects of water on

building fabrics it is better to properly manage it at the early stages and early detection or

confirmation of its purity to ensure quick action before its full usage [13].

2.3.3.1 Quality of Water for production of Concrete (Mixing Water)The common criteria or yardstick to the suitability of water for preparing concrete is that water

fit for human consumption is also fit for concrete making. But this yardstick is not true for all

conditions. Water containing 0.05% sugar by weight of cement is quite fit for drinking, but it

retards cements initial setting time by 4 hours. Thus water to be used for concrete production

should not contain substances which may have appreciable harmful effect on the initial setting

time, strength and durability of concrete. Substances like oil, acids, carbonates, and bi-

carbonates, alkalis, sugar, silt and organic materials have been found to have harmful effect on

the properties of the fresh and hardened concrete. Hence concrete mixing water should be free


Addis Ababa University, AAiTPage xix

from these impurities. The PH value of concrete mixing water should be between 6 and 8. A dark

color or a smell does not necessarily mean that the water contains deleterious materials [4].

Rivers carrying large concentration of suspended solids, industrial and domestic waste, streams

and wells in mining and arid alkaline areas should be viewed with suspension and the effect of

such waters should be determined before the use in actual construction. This problem is highly

observed in Ethiopia and most of the rivers are polluted by this factory wastes. The effluents

from this paint, textile, fertilizer and sugar factories and sewage works and gas works have been

found to have harmful effect on concrete. Hence the quality water that will be used for concrete

production should be well known before using it for concrete production [15].

2.3.3.2 Effect of Water Impurities on Properties of Concretei. Carbonates and Bicarbonates of potassium and sodium: -the carbonates and bicarbonates

of sodium and potassium affect the setting time of cement. The presence of sodium carbonate

accelerates the setting time, while bicarbonates may either accelerate or retard the setting of the

cement. The higher concentrations of these salts will reduce the concrete strength considerably.

Salts of manganese, tin, zinc, copper and lead reduce the concrete strength to a great extent.

Sodium salts reduce the initial strength of concrete to an extraordinarily high degree. Sodium

sulphide also deteriorates the strength of concrete.

ii. Algae: - it may be present on the surface of aggregate or in mixing or washing water. It

combines with cement forming a layer on the surface of aggregate and reduces the bond between

the cement paste and aggregate. Also, algae have the air entraining effect in large quantities in

the concrete resulting in lowering the strength of concrete

iii. Use of Sea Water in Mixing Concrete:- Sea water contains about 3.5% salinity. This

salinity contains about 78% sodium chloride and 15% chlorides and sulphates of magnesium.

Sea water also contains small quantities of sodium and potassium salts which can react with

aggregates in the same way as alkalis in the cement. Thus if aggregates are found alkali reactive,

then sea water should not be used even for the production of plain cement concrete. The use of

sea water to mix concrete does not reduce the strength of concrete appreciably, but it may lead to

corrosion of reinforcement in certain conditions. Sea water is known to accelerate the early

strength of concrete slightly, but reduces the 28 days strength by 10–15%. Sea water containing


Addis Ababa University, AAiTPage xx

large quantities of chlorides may cause efflorescence and constant dampness in the structure.

Thus where appearance is important, seawater should not be used for concrete mixing. The use

of sea water is also not advisable in plaster work where the surface is likely to be painted on a

later date [1,4,6].

Table -2.2 shown below summarizes the permissible limits of impurities in water for use of

concrete production.

Table 2-2 limits of permissible impurities in water Source: [6]

2.3.3.3 Water for Curing of ConcreteWater suitable for mixing concrete is also suitable for curing of concrete. Curing water should

not produce any objectionable stain or unsightly deposition the surface. Iron and organic matter

in the water are chiefly responsible for staining or discoloration and especially when concrete is

subjected to prolonged wetting, even a very low concentration of these can cause staining.

The requirements for curing water are less stringent than those discussed above, mainly because

curing water is in contact with the concrete for only a relatively short time. Such water may

contain more inorganic and organic materials, sulfuric anhydride, acids, chlorides, and so on,

than acceptable mixing water, especially when slight discoloration of the concrete surface is not

objectionable. Nevertheless, the permissible amounts of the impurities are still restricted. In

cases of any doubt, water samples should be sent to a laboratory for testing and

Type of Impurities Permissible percentage ofsolids by weight of water

Organic Impurities 0.02

Inorganic impurities 0.3

sulphates 0.05

Alkali ChloridesFor Plain concrete 0.2

For Reinforced Concrete 0.1


Addis Ababa University, AAiTPage xxi

recommendations. Water for washing aggregates should not contain materials in quantities large

enough to produce harmful films or coatings on the surface of aggregate particles [4].

2.3.4 AdmixturesAdmixtures are materials other than the basic ingredients of concrete added to the concrete mix

immediately before or during the mixing process to modify one or more specific properties of

concrete in fresh or hardened state. Anosike (2011) asserted that, the use of admixtures should

offer improvement in the properties of concrete by adjusting the proportions of cement and

aggregates. However, it should not affect adversely any property of concrete. He also further

asserted, an admixture should be used only after assessing its effect on the concrete to be used

under an intended situation. Tests on the representative samples of the concrete materials for a

particular concrete should be conducted in order to get dependable information on the properties

of concrete containing admixtures. It should also be known that admixtures are no substitute for

good workmanship i.e. the effect of bad workmanship cannot be improved by the use of

admixtures [4,6].

Currently there are different and many types of admixtures are produced from different suppliers

around the world in order to improve various properties of fresh or hardened concrete. Such as

admixtures which accelerate the initial setting and hardening of concrete, retard the initial setting

of concrete, increase the strength of concrete, improve the workability of fresh concrete, improve

the durability of concrete, control the alkali aggregate expansion, reduce shrinkage during setting

of concrete, increase the bond between old and new concrete surfaces and also between concrete

and reinforcement and etc [1,3,4,6].

2.4 Fresh ConcreteFresh or plastic concrete is a freshly mixed material which can be moulded into any shape. The

relative quantities of its ingredients such as cement, fine and coarse aggregates and water mixed

together controls its properties in wet or green state as well as in hardened state. The plastic state

of fresh concrete provides a time period for transportation, placing, compaction, and surface

finishing. The properties of fresh concrete have a large influence on construction speed and

decision making [4].

The properties of fresh concrete are short-term requirements in nature, hence they should be

easily mixed and transported, shall be uniform throughout a given batch and between batches,


Addis Ababa University, AAiTPage xxii

must keep its fluidity during the transportation period and it should have flow properties such

that it is capable of completely filling the forms. Since compaction plays an important role in

ensuring the long-term properties of the hardened concrete it must have the ability to be fully

compacted without segregation and it must be capable of being finished properly, either against

the forms or by means of troweling or other surface treatment [4].

2.5 Production of Concrete

2.5.1Specifying ConcreteConcrete can be specified in one of the three common ways. These are Designed Mix, Prescribed

Mix and Standard Mix.

Designed Mix: In this case, the mix is specified by a grade corresponding to required

characteristic compressive strength at 28 days. In addition to stating the strength grades the

purchaser must also specify any particular requirements for cement and aggregate content and

maximum free water/cement ratio.

Prescribed Mix: This is a recipe of constituents with their properties and quantities used to

manufacture the concrete. The concrete specifier/designer must state: the type of cement, type of

aggregates and their maximum size, mix proportions by weight, the degree of workability (slump

and or water cement ratio) and the application. Prescribed mixes are based on established data

indicating conformity to strength, durability and other characteristics.

Standard Mix: Mix composition and details are specified by: cement to aggregate by weight,

type of cement, aggregate type and maximum size, workability and use or omission of

reinforcement. These mixes are most suited to site production, where the scale of operations is

relatively small. They may be used where mix design procedures would be too time consuming,

inappropriate or uneconomic.

2.5.2 Concrete Production ProcessProduction of quality concrete requires thorough care exercised at every stage of manufacture of

concrete. It is interesting to note that the ingredients of good concrete and bad concrete are the

same. If proper care is not exercised and good rules to produce concrete are not observed, the

resultant concrete is going to be of bad quality. With the same material if intense care is taken to


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exercise control at every stage, it will result in good concrete. Hence, it is essential to know each

stage of manufacture of concrete and preventive measures to be taken for producing good quality

concrete. The various stages of manufacture of concrete are: Batching, Mixing, Transporting,

Placing, Compacting, Curing and Finishing. Each stages of concrete production will be presented

in succeeding sub topics.

2.5.2.1 BatchingThe correct measurement of the various materials used in the concrete mix is called batching.

Errors in batching are partly responsible for the variation in the quality of concrete. The accuracy

of measuring the ingredients affects the quality of the concrete produced, and is largely

dependent on the selected batching method [16]. There are two main objectives of batching

irrespective of the batching method selected. The first is to obtain uniformity and homogeneity in

the physical properties of the concrete, such as, unit weight, slump, air content, strength, and air

free unit weight of mortar in both individual and successive batches of the same mixture

proportions. The second is to maintain proper sequencing and batching of the ingredients. To

meet these objectives, proper batching plant, adequate inspection and supervision of the batching

processes are required. Generally concrete can be batched in two ways these are volume batching

and mass (weight) batching.

Volume Batching: In this method, the materials are measured by volume using a gauge box.

Volume batching is not a good method for proportioning the material because of the difficulty it

offers to measure granular material in terms of volume. If the fine aggregate is damp or wet its

volume will increase by up to 25% and therefore the amount of fine aggregate should be

increased by this amount. This increase in volume is called “bulking”. Each bag of cement as

delivered by the factories is packed to contain a net weight of 50kg.

In Ethiopia, volume batching is mostly adopted even for large cast in situ concreting operations

and mostly they use box size 50x40x20, 18,16cm according to the grade of concrete to be

produced. Hence, as far as batching by volume is practiced in the country adjustments has to be

done for the moisture present in sand which results in its bulking and adjustments to the amount

of water depending on the absorption capacity and the free moisture content of the sand and the

coarse aggregate.


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Weight Batching: In weight batching aggregates, cementitious materials and powder admixture

(if any) are measured by weight; water and liquid admixtures are measured by volume or weight.

This method involves the use of a balance which is linked to a dial giving the exact mass of the

materials as they are placed in the scales. This is the best method since it has a greater accuracy

and the balance can be attached to the mixing machine [1,2].

2.5.2.2 Mixing

Having placed the correct amount of materials into the mixer, thorough mixing is essential for

the production of uniform quality concrete. The mixing should ensure that the mass becomes

homogeneous, uniform in color and consistency by mixing all ingredients thoroughly. Thorough

mixing means distributing the concrete ingredients uniformly and spreading the cement-water

paste evenly onto the surfaces of the aggregates. If this is not achieved, the quality of the

concrete discharged will not be the same throughout the mix. There are two methods adopted for

mixing concrete namely hand mixing and machine mixing [1,16].

Hand Mixing: Mixing of concrete by hand is less efficient than mixing by machine but on small

works hand mixing is still practiced. Concrete mixing by hand should never be done on the

ground, as earth and dirt dry grass, leaves, etc will mix with it. It always should be done over an

impervious concrete or brick floor.

The materials should be thoroughly mixed in the dry state before the water is added. The water

should be added slowly, until a uniform color is obtained. As the mixing cannot be thorough and

efficient, it usually results in poor concrete of lower strength. Hence to compensate for the lower

strength it is advisable to allow an extra 10% of cement above that normally required.

Machine mixing: Mixing of concrete is almost regularly carried out by machine, for reinforced

concrete work and for medium or large scale mass concrete work. Machine mixing is quicker,

more efficient and produces much more homogeneous concrete. The mix should be turned over

in the mixer for at least two minutes after adding the water. The first batch from the mixer tends

to be harsh since some of the mix will adhere to the sides of the drum [13].

Both mixing methods are commonly practiced in Ethiopian construction industry but machine

mixing using drum mixers are the most common practice for Class I concrete grades.


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The workmanship of the mixing greatly affects the uniformity of the concrete produced. There

are different factors that affect the uniformity of mixing. These are, the way of loading to the

mixer, mixing time, discharging the mixer, capacity of the mixer, formation of cement balls,

formation of head packs, mechanical conditions, design of the mixer and retempering are the

most important factors which affect uniformity of concrete produced while mixing [15].

Concrete Mixing Time: On site, there is often a tendency to mix concrete as rapidly as possible,

and hence, it is important to know the minimum mixing time necessary to produce concrete of

uniform composition and consequently, of reliable strength. The optimum mixing time depends

on the type and size of mixer, on the speed of rotation and on the quality of blending of

ingredients during charging of the mixer. Generally, a mixing time of less than one to one

minutes fifteen seconds (1min.-1min.15sec) produces appreciable non-uniformity in composition

and a significantly lower strength; mixing beyond two minutes (2min.) causes no significant

improvement in these properties [6]. Table-2.3 below shows different recommended mixing time

for different capacity of mixers.

Table-2.3 Recommended Concrete Mixing Time Source: [2, pp126]

Capacity of Mixer(m3) Mixing Time(minutes)0.8 11.5 1(1/4)2.3 1(1/2)3.1 1(3/4)3.8 2

4.6 2(1/4)7.6 3(1/4)

Generally, if mixing takes place for over a long period, evaporation of water from the mix can

occur, with a consequent decrease in workability and an increase in strength. A secondary effect

is that of grinding of the aggregates, particularly if soft, the grading thus becomes finer and the

workability lower. In the case of air-entrained concrete, prolonged mixing reduces the air content

by 1/10 of its value/hr [2].

2.5.2.3 Transporting and placing of ConcreteEven though concrete may be proportioned and mixed properly, its quality may be seriously

impaired by the use of improper or careless transporting and placing methods. The method used


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for transportation should deliver the concrete to its final location efficiently without significantly

altering its properties.

Concrete should be transported and placed at its desired position as quickly as possible without

segregation, drying, etc. As soon as concrete is discharged from the mixer, internal as well as

external forces start acting to separate the dissimilar constituents. If over-weight concrete is

confined in restricting forms, the coarser and heavier particles tend to settle and finer and lighter

materials tend to rise. If concrete is to be transported for some distance over rough ground the

runs should be kept as short as possible since vibrations of this nature can cause segregation of

the materials in the mix.

Concrete is usually transported through different equipments to place in its position. Some of

transportation equipments are Wheelbarrow, buckets, agitating trucks, non-agitating trucks,

chutes, belt conveyors, dumpers, concrete pumps, hoists etc. To guarantee good quality concrete,

proper transporting and handling is required. Celik and Shetty agreed that factors which affect

the quality of concrete through transporting and placing are slump loss, loss of ingredients,

segregation and formation of cold joints.

i. Slump Loss: All concretes lose slump. Otherwise, concrete would never harden. The concrete

first gradually loses its all slump and then proceeds to harden through the initial and final set and

this is known as "normal slump loss". But when concrete loses its workability before placing to

such an extent that, placing and compaction cannot be undertaken as specified, then this slump

loss is abnormal and this is said to be "slump loss"[1,16].

When the slump loss exceeds the permissible limit, it usually causes significant difficulties. The

production rate and the quality of workmanship both decrease. Eventually, the cost goes up and

repair for imperfections will be obligatory.

When repairs become necessary, the appearance of the concrete is inevitably diminished. Thus,

slump loss can be a serious construction problem. Excessive delivery times and high temperature

are major causes of slump loss [1].

ii. Loss of Ingredients: During transporting and placing, the concrete ingredients may be lost.

This is usually happen when we use open top transporting equipments such us wheel barrows on


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rough terrain. As a result, the concrete transporting container needs to be watertight and should

avoid loss of ingredients which may result in poor concrete production.

iii. Segregation: Segregation can be defined as separation of the constituents of a heterogeneous

mixture so that their distribution is no longer uniform. In fresh concrete, segregation is caused by

differences in the size of particles and sometimes in the specific gravity of the ingredients. Fresh

concrete may segregate in two ways. Firstly, the coarse particles tend to separate since they

travel further along a slope or settle more than the finer particles. Secondly, the paste separates

the other constituents. This may bring a poor quality of concrete which may be porous, hard to

finish and poor layers formation and poor resistance to wear [1,4].

iv. Cold Joints: The rate of transporting and placing concrete should be enough to prevent the

formation of cold joints in the structure. Cold joints occur when a layer of previously placed

concrete hardens or sets to such a degree that, a newly placed concrete layer does not bond to it.

Hence, if cold joints are unavoidable, it is recommended that, a richer thin mortar layer is placed

on the hardened concrete, and then, the normal concrete is placed on that mortar layer. This soft

bed reduces the voids between the two layers.

2.5.2.4 Compaction of ConcreteCompaction of concrete is the process adopted for expelling the entrapped air from the concrete.

In the process of mixing, transporting and placing of concrete air is likely to get entrapped in the

concrete. The lower the workability, higher is the amount of air entrapped. In other words, stiff

concrete mix has high percentage of entrapped air and, therefore, would need higher compacting

efforts than high workable mixes [1].

Compaction is one of the most significant concrete production phases that determines both the

strength and durability of concretes. Since compaction helps to remove the entrapped air from

the fresh concrete, removing this entrapped air and rock pockets will improve the strength,

durability and appearance of the concrete.

A higher concrete quality can be obtained with a lower water/cement ratio provided that,

sufficient compaction is maintained. However, insufficient compaction will reduce the quality of

dry concrete at a higher rate than of wet concrete. Proper compaction of concrete is essential to


Addis Ababa University, AAiTPage xxviii

reduce the adverse effects of entrapped air on the quality of concrete. It is well established that,

each percent of entrapped air (including the entrained air) reduces the strength of concrete by

about 5 to 6%. The imperfections of compaction do not only affect the strength of the concrete,

but the durability and the appearance of concrete are also drastically diminished.

Improper compaction can cause troublesome imperfections. The most common compaction

imperfections are honeycombing and excessive entrapped air voids which results in poor

concrete production. To maintain the desired concrete quality, it is necessary to consider the

selection of compaction method, equipment vibration duration, vibration techniques and re-

vibration [1,2].

Re-vibration of concrete

Re-vibration is an application of vibration to compact concrete after placing and initial

compaction, but preceding initial setting of the concrete. The unintentional vibration of the

bottom layer while placing and compacting the successive layer is not considered to be re-

vibration. Re-vibration is beneficial if the concrete is again brought to a plastic condition. It may

be accomplished by internal vibrators or form vibrators and should be done as late as possible

after placing the concrete, providing that, the concrete still can be in its plastic state [4].

Celik (1989) states that, re-vibration results in improving the 28 day compressive strength of

concrete by about 14%, when it is carried out about 1-2 hr after placing and it also improves the

reinforcement bond strength, reduces the content of entrapped air, and relieves plastic shrinkage

stresses [16]. The same study states that, re-vibration is particularly beneficial for the top 500 to

1000 mm of a placement, where the water voids are the most prevalent. Wetter concretes can be

improved considerably by re-vibration.

2.5.2.5 Finishing of ConcreteThere are two kinds of concrete voids namely, water void and air void. Honey-combed concrete

does not develop good bond with reinforcement. Water may penetrate through these voids and

corrode the steel. The operations adopted for obtaining a true and uniform concrete surface are

called finishing operations. A tamper usually leaves a slightly ridged surface. Thus it needs

finishing [4].


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Finishing is one of the most important factors that affects the quality and serviceability of a floor

or slab. Without special precautions, the top surface of a concrete floor or slab can suffer from

reduced quality. To avoid reduced quality for finishing floors and slabs, screeding, floating and

finally trowelling process helps significantly. Screeding refers to a leveling operation which

removes bumps and hollows and gives a true and uniform concrete surface. Floating is the

operation of removing the irregularities from the surface of the concrete left after screeding.

Trowelling is the final operation of finishing done where smooth surface is desired. Trowelling

should be done after the evaporation of water from the concrete surface. Types of surface

finishing's to concrete can be tamped finish, brush finish, wooden float finish and steel trowel

finish. Concrete finishing plays vital role in achieving quality of concrete. Therefore, proper

concrete finishing methodologies and quality control should be practiced [13].

2.5.2.6 Concrete CuringConcrete curing is the method of maintaining suitable moisture content and a favorable

temperature in concrete during the period immediately after the placement of concrete so that

hydration of cement may continue till the desired properties are developed sufficiently to meet

the requirements of service. The reasons for curing concrete are to keep the concrete saturated or

as nearly saturated as possible, until the originally water filled space in the fresh cement paste

has been filled to the desired extent by the product of hydration of cement, to prevent the loss of

water by evaporation and to maintain the process of hydration, to reduce the shrinkage of

concrete and to preserve the properties of concrete [1,2].

The requirement of curing comes from the fact that hydration of cement can take place only in

water filled capillaries. Due to this reason, a loss of water by evaporation from the capillaries

must be prohibited. Further water lost internally by self-dehydration has to be replaced by water

from outside. Water required for chemical reaction with cement i.e. for hydration is about 25 –

30% of water added to the cement; the rest of the water is used for providing workability and

help to continue hydration [1,13].

There are different methods are used to cure concrete. These methods of curing depend upon the

nature of work and atmospheric conditions. Generally, there are two common systems of

maintaining the presence of the required water for the hydration of the cementitious material

which initially is furnished by the mixing water in the concrete. The first one is a moist


Addis Ababa University, AAiTPage xxx

environment from the continuous or frequent application of water through ponding, sprays,

steam, or saturated cover materials such as burlap or cotton mats, rugs, earth, sawdust, straw or

hay, and the second is the prevention of loss of mixing water from the concrete by means of

sealing materials such as impervious sheets of paper or plastic, or by the application of a

membrane forming curing compound to the freshly placed concrete. Care must be taken to

ensure that saturated cover materials do not dry out and absorb water from the concrete [1, 2].

2.6 Concrete Quality ManagementThe quality of a finished concrete structure is affected by the quality of the freshly mixed

concrete and the standard of workmanship in handling, compacting, finishing, and curing the

concrete. The standard of workmanship throughout the concreting operations is therefore

extremely important in construction of a good quality concrete structure. Unfortunately although

materials are regularly checked, monitored and tested, the workmanship which is harder to

specify and quantify is often given little attention or ignored completely. To improve quality of

concrete, producers needs to put all factors that affect concrete quality together into a quality

management system (QMS) and adhere to it. A quality management system establishes company

policy and goals and sets actions and responsibilities for individuals within an organization with

regard to quality. Stakeholders who directly or indirectly affected by the end product of concrete

structures should also participate in enhancing the quality of concrete production. It is the

intention of this part of the research to discuss the aspects of quality management principles

which can be applied in concrete production.

2.6.1 Definition of QualityQuality is the ability of a product or system to satisfy all the requirements it was designed to

meet. Ceilik (1989) states concrete quality as the "degree of excellence", which is generally

established in the project specifications. Rakish also stated that quality is not perfection but,

merely fitness for the purpose. Hence the best concrete for any given purpose is the one that does

the job satisfactorily at the lowest cost. Ceilik clearly states that, quality concrete is that which is

capable of meeting the requirements of the job in terms of strength, durability and appearance.

Strength is often the major feature in defining the quality of concrete because strength is both

easy to define and to measure in concrete production. Consequently in many cases, strength is

the unique measurement of concrete quality [16, 17].


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Building construction project involves in an extremely complex process, relating a wide range of

activities and concrete construction takes a major part of it. Therefore, enhancing the quality of

concrete greatly helps the overall improvements of quality of the project. There are different

factors affecting the quality of concrete construction, such as design, materials, machinery,

topography, geology, hydrology, meteorology, construction technology, methods of operation,

technical measures, management systems and so on. Since quality is a complex multi-component

product made up of several systems, construction companies must adhere to the principle of

quality first, and persist on quality standards with the core of artificial control and prevention to

provide more high quality, safe, suitable, and economic composite products.

Quality should be properly managed in concrete production to obtain the intended requirements

by the customer. Hence quality control is critically essential throughout concrete production.

Patel, Pitroda and Rekish agreed that, if there is no quality control, there is no economic benefit

obtained from any construction. They further said that implementing quality management in the

course of building construction can effectively prevent the safety accidents to occur during the

latter process of the use of building products. The succeeding part briefly discuss about basic

principles in project quality management to improve the quality of concrete products which

strongly helps to manage concrete production [17].

2.6.2 Quality Management

Quality is the degree to which a set of inherent characteristics fulfill requirements. Stated and

implied needs of customers are the inputs to develop project requirements. Quality management

involves a continuous search for ways to prevent defects by “doing the job right”. Quality

management is concerned with preventing problems by creating the attitudes and environment

that make prevention possible. A critical quality management in the project context helps to turn

stakeholder needs, wants, and expectations into requirements. Therefore the application of

project management principles in concrete production becomes mandatory since it is major part

of any building construction projects [20].

Project quality management includes all the processes and activities of the performing

organization that determine quality policies, objectives, and responsibilities so that the project

will satisfy the needs for which it was undertaken. It implements the quality management system


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through the policy, procedures, and processes of quality planning, quality assurance, and quality

control, with continuous process improvement activities conducted throughout, as appropriate.

The project quality management process includes three basic stages which help in improving

quality production. The first is quality planning and refers to identifying which quality standards

are relevant to the project and determining how to satisfy them. The second is performing quality

assurance; this stage helps in applying the planned, systematic quality activities to ensure that the

project employs all processes needed to meet requirements. The third and final stage is

performing quality control which greatly helps in monitoring specific project results to determine

whether they comply with relevant quality standards and identifying ways to eliminate causes of

unsatisfactory performance. Hence, applying these three quality management processes in

concrete production greatly helps to enhance the quality of concrete produced at site [7].

2.6.2.1 Quality PlanningQuality planning involves identifying which quality standards are relevant to the project and

determining how to satisfy them. It is usually one of the key processes when doing the planning

process and during development of the project management plan. Quality standards are usually

the specification which describes the requirements of the client and stated regulatory standards.

If C-30 concrete is specified by the client, to achieve this requirement proper planning for the

material to be used, suitable production process ,the workmanship and other factors which affect

the quality of concrete is crucial because "fail to plan is planning to fail''[13].

Quality planning shall be done in the course of developing quality management plan. Project

Quality plan is a crucial document that any contractor or consultant must have. It describes all

the life line of a project that will ensure the end product that is going to be delivered to client

meet all the requirement and specifications. Experiences show that, most of consultants and

contractors found in Ethiopia do not have any idea on how to come out with this project quality

management plan. Therefore, efforts should be employed on understanding of quality

management plan and its relevance.

Quality planning should consider cost-benefits tradeoffs and cost of quality (COQ). The primary

benefit of meeting quality requirements is less rework, which means higher productivity, lower

costs, and increased stakeholder satisfaction. Juran (2011), described quality costs as the total

costs incurred by investment in preventing nonconformance to requirements, appraising the


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product or service for conformance to requirements, and failing to meet requirements (rework).

Failure costs are often categorized into internal and external. According to Feigenbaum (1991),

internal failure costs are costs arise from defects caught internally and dealt with by discarding or

repairing the defective items such works are scrap, rework material procurement costs. He also

describes external failure costs are costs which arises from defects that actually reach customers

such as complaints in warranty, complaints out of warranty, product service, product liability,

product recall, loss of reputation.

Failure costs are usually referred as cost of poor quality. Harrington (1987) defined poor quality

cost as all the cost incurred to help the employee do the job right every time and the cost of

determining if the output is acceptable, plus any cost incurred by the company and the customer

because the output did not meet specifications and/or customer expectations. Therefore quality

should be critically planned to avoid any expenses that arise from poor quality for the contractor

and the client who is the end user of the product [32].

Though quality planning of any product is compulsory to fulfill the intended requirements and

avoid any costs that arise from poor quality; the cost to get a quality product should be as

minimum as possible. Figure 2.1 below shows a relationship between cost of poor quality and

cost of quality program. As shown in the figure below, in producing high quality product the

cost, the cost of quality program should be as minimum as possible so that it is possible to obtain

optimal point.

Fig 2.1 - Balanced Cost of Quality chart Source: [32, pp16]


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2.6.2.2 Quality Assurance (QA)

Quality assurance (QA) is the application of planned, systematic quality activities to ensure that the

project will employ all processes needed to meet requirements. It is also described as evaluating

overall project performance on regular basis to provide confidence that the project will satisfy the

relevant quality standards [7].

In concrete production quality assurance is the responsibilities of all stakeholders who participate in

the production process such as the contractor, consultant and client. Quality assurance recognizes

professional bodies who participate in the project and regulatory agencies as people on production

line, working as a team to achieve a common goal. Their quality control roles will require setting

standards, checking and monitoring of production which will lead to a product of a consistently

satisfactory standard quality.

2.6.2.3 Quality Control (QC)Quality control in the production process is a major ingredient which involves checking and

reviewing work that has been done, inspection, testing and sampling to ensure good product

delivery. Performing quality control (QC) involves monitoring specific project results to

determine whether they comply with relevant quality standards and identifying ways to eliminate

causes of unsatisfactory results. Quality control is not a onetime duty rather it should be

performed throughout the project life time. It is often performed by a quality control department

or similarly titled organizational unit. In concrete production the quality control work is usually

undertaken by supervisory bodies that are hired by the owner. Quality control can include taking

action to eliminate causes of unsatisfactory project performance [7].

Quality control is the application of all the measures that are taken during material selection,

concrete production processes and on finished concrete products to ensure the compliance of the

works with the specification. The cost of achieving quality requirements during the construction

phase is directly proportional to the cost of skilled labor, materials, equipment method and

supervision utilized as well as to the cost of monitoring and inspecting the work to verify the

output quality and to correct or repair defective work [13].


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It also expressed mathematically, the cost of achieving quality at construction phase is directly

proportional to the resources employed for the tasks, i.e.

= ( + + +⋯… . . + )……………… [Eq. 2.1]

= + + + + ………………..……. [Eq. 2.2]

Where, = Cost of achieving quality at construction phase,

= cost of skilled labor,

= cost of materials,

= cost of plants & equipment and method of utilization,

= supervision, in line with specified standards and best global practice,

= monitoring & inspection of works in progress.

According to this study, the absence of any of these quality requirement variables for any given

concrete production activity undermines the desired standard result. Another literature also

agreed that, in order to achieve quality on a construction activity such as concrete work on site,

stakeholders must team up to achieve the set goal. Therefore, all stakeholders who participate in

concrete production should give attention for quality control of overall concrete production [10,

13].

The reason of quality control of concrete is to measure and control the variation of those

operations which affect the strength or the uniformity of concrete: batching, mixing, formwork

design and construction, placing, compaction, curing, and testing. According to Arum (2008), a

good quality concrete can be obtained by effectively controlling both human and non-human

factors. According to him, human factor refers to effective supervision and good workmanship

while non-human factor refers to the materials used in concrete production.

Quality control in construction shall be done through experts who have better knowledge on

construction. As different literatures agreed that, the quality of concrete is dependent on different

parameters such as the quality of each ingredients, the production process and workmanship.

Hence, quality control methods undertaken on each parameter are greatly crucial and strongly

help to minimize the degree of obtaining poor quality concrete. The usefulness of quality control

of concrete production is not only in the compliance with specifications but also in reduction of

production cost for the concrete producer [16,17,18].


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Generally quality management system helps to provide a quality product that fits to its purpose.

Hence it is crucial to use quality management processes in concrete construction to obtain a good

quality of concrete. Quality management shall be carefully planned in to a quality management

plan document and all stakeholders shall work in collaboration to address the intended quality.

It should be understood that quality management process is not one time end process rather it

should be carefully examined and revised based on the actual problems and facts. It always needs

the application of PDCA cycle (i.e. planning, doing, controlling and acting). Therefore, through

serious control of quality it is possible to obtain the intended quality product.

2.6.2.4 Statistical Quality Control of ConcreteThe basis for statistical quality control (SQC) in concrete production or any other industry

depends upon a thorough knowledge of the sources of variation affecting the product being

subjected to control [22]. In concrete production, quality control is usually done based on 28

days of compressive strength tests. The strength of concrete has an inherent variability as it

depends on the variations in properties of concrete and variations due to testing methods [21].

Principal sources of strength variations are summarized in the Table 2.4 below.

Table 2.4 Principal sources of strength variations in concrete production and quality testing

Variations due to the properties of concrete Variations due to testing methods

Changes in w/c ratio caused by

o Poor control of water

o Excessive variation of moisture in

aggregates or variable aggregate

moisture measurement

Variations in water requirement caused by:

o Changes in aggregate grading,

absorption, particle shape

o Changes in cementitious and admixtures

properties

o Changes in air content

o Improper sampling procedures

o Variations due to fabricated mould:

poor quality, damaged or distorted

moulds

o Changes in curing:

o Temperature variation

o Variable moisture control

o Delays in bringing cylinders to

the laboratory

o Delays in bringing standard

curing


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o Delivery time and temperature changes

Variations in characteristics and production

process:

o Variation in batching, mixing,

transporting, placing, compacting and

finishing.

o Variation in temperature and curing

Poor testing procedures:

o Specimen preparation

o Test procedure

o Uncalibrated testing equipment

A strength test result is defined as the average strength of all specimens of the same age,

fabricated from a sample taken from a batch of concrete. Concrete tests for strength are

typically treated as if they fall into a distribution pattern similar to the normal frequency

distribution curve illustrated in Fig. 2.2

Fig 2.2 - Normal frequency curves for three different distributions with the same mean but

different variability. Source (ACI 214, 1990)

When there is good control of concrete production, the strength test values will tend to come

together near to the average value, that is, the histogram of test results become tall and narrow as

shown in curve1 of figure 2.2. As variation in strength results increases, the spread in the data

increases and the normal distribution curve becomes lower and wider this may tend to indicate

Curve 1

Curve 3

Curve 2


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poor quality concrete. The Ethiopian building codes of standards (EBCS 2-1995) stipulates only

5% defectives are allowed and 95% of the test results should confirm above the characteristics of

concrete. The normal distribution can be fully defined mathematically by two statistical

parameters: the mean and standard deviation. These statistical parameters of the strength can be

calculated as shown below:

= ∑ = ( + + ………+ )…………… [Eq. 2.3]

Where the i-th strength test result and n is is the number of tests in the record.

Standard deviations(S) are the most generally recognized measure of dispersion of the

individual test data from their average and it can be calculated by the formula given below.

=∑

……………….…....................... [Eq. 2.4]

Where is the sample standard deviation, n is the number of strength test results in the records,

is the mean or average strength test results.

Coefficient of variation (V) is the sample standard deviation expressed as a percentage of the

average strength is called the coefficient of variation and it can be calculated as

V = ∗ 100……………………............................[Eq. 2.5]

Where is the coefficient of variation is the sample standard deviation and is the sample

average strength of test results.

2.6.2.5 Standard Control and Compliance Criteria’s for ConcreteThe principal purposes of statistical evaluation of concrete data are to recognize sources of

variability. This data can then be used to determine appropriate steps to maintain the desired

level of control. One simple approach of statistical control is to compare overall variability and

within-test variability, using either standard deviation or coefficient of variation, as appropriate.

ACI 214 states different standard control which are appropriate to concrete and the tables below

summarize standard deviation and coefficient of variation for different control standards.

Table 2.5 Standard deviation for different control standards, Source ACI 214

Overall Variation


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Class of operationStandard deviation for different control standards, MPa

Excellent Very Good Good Fair Poor

General construction testing Below 2.8 2.8-3.4 3.4-4.1 4.1-4.8 Above 4.8

Laboratory trial batch Below 1.4 1.4-1.7 1.7-2.1 2.1-2.4 Above 2.4

Table 2.6. Coefficient of variation for different control standards, Source ACI 214

Overall Variation

Class of operationCoefficient of variation for different control standards (%)

Excellent Very Good Good Fair Poor

General construction

testing Below 7 7-9 9-11 11-14 Above 14

Laboratory trial batch Below 3.5 3.5-4.5 4.5-5.5 5.5-7 Above 7

Any specified concrete strength, should have a tolerance for test results conducted for quality

control. It is impractical to specify an absolute minimum strength, because there is always the

possibility of even lower strengths simply due to random variation, even when control is good.

There will always be a certain probability of tests falling below characteristic strength of

concrete. British standard (BS 5328:1990), American Concrete Institute Association (ACI 318),

Indian standards (IS 456:2000), and most other building codes and specifications establish

tolerances for meeting the specified compressive strength acceptance criteria. Ethiopia also has

building code of standards called EBCS-2:1995 which establish tolerance for meeting the

specified compressive strength acceptance criteria. According to EBCS-2:1995, two compliance

criteria’s are specified.

Criterion 1: This criterion may be applied in all cases but is less suited to large scale sampling

each lot is represented by three samples, the strength of which are X1< X2< X3.According to the

code, a lot is accepted if the following conditions are satisfied simultaneously.


Addis Ababa University, AAiTPage xl

≥ + .……….......….…………............................…[Eq. 2.6]

≥ − ………………………………….................… [Eq. 2.7]

Where, m3 is the mean value

Fck is the specified characteristic strength

K1& K2 are the margins of strength given in the table below.

X1 is the average strength of the minimum strengths for the several lots

Table 2.7 Margins of Strength in MPa, Source: EBCS-2:1995

Margin of strength First two lots Third and Fourth Fifth lot and above

K1 5 4 3

K2 1 2 3

Criterion 2:- this is suitable for large lots. Each lot is represented by not less than 15 test

specimens and the lot is accepted if the following conditions are satisfied simultaneously.

− ≥ …………………………...................… [Eq. 2.8]

≥ − ..…………………….…………...........…. [Eq. 2.9]

Where mn = is mean value

Sn is standard deviation of set of sample result

fck is the characteristics strength

K2 is the margin of strength (may taken as 4MPa)

λ is coefficient (may be taken 1.4 MPa)

n is number of specimens

In case of the test results do not satisfy the requirements of the selected acceptance criterion,

EBCS -2:1995 recommends measures to be in use.

1. By identifying the structure with defect, do necessary checking of structural safety using

appropriate calculations.

2. Check tests by non-destructive methods are applicable to hardened concrete in the

finished parts of a structure or in precast unit.


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2.7 Concrete Production Practice in EthiopiaDifferent researches show that, the construction industry in all developing countries should

improve. Many writers state that governments are responsible for the construction industry

development, however, Anosike (2011) argues that not only government but also construction

enterprises and practitioners can contribute to efforts to improve the industry. He suggested two

improvement areas; one is the need of continual reviewing of building regulations and standards

drafted in the form of technical aids rather than restrictive rules and in a language appropriate to

the educational background of the majority of the users. The other is the need of construction

enterprises to improve their productivity, efficiency, quality of work and innovation as corporate

objectives, and set up appropriate organizational structures to achieve them. Since Ethiopia is

one of the developing countries in the world with the fastest growth rate, improvements in the

quality of the construction industry is mandatory.

The construction industry in Ethiopia is boosting in high growth rate due to the need for

infrastructures and other business sectors in the country. It contributes about 7.6% of the

country’s GDP as reported on 2014. Though there is a high growth rate in the construction

industry of Ethiopia, most of mega projects are executed with foreign contractors due to lack of

enough skilled professionals and inexperienced workmanship.

Concrete production in Ethiopia is not that much automated. Most of the building projects exist

throughout the country uses cast in situ concrete for building structures but currently ready

mixed concrete production and suppliers are emerging in urban areas of the country in significant

amount. The production process of cast in situ concrete is accomplished on site manually. Every

production processes are usually done through unqualified laborers. Even most constructors are

not fully equipped and well organized. Therefore, with all those reasons the quality of concrete

and overall buildings quality may greatly varies from project to project. This situation is

observed commonly in public projects such as condominium projects. UN-HABITAT in its 2011

report pointed out that management of specific issues like location, built environment design,

and construction quality are unanticipated challenges of the program. The same report expressed

that if not addressed properly, the mentioned challenges might endanger the long-term success of

the program.


Addis Ababa University, AAiTPage xlii

The integrated housing development program is the one among available mega and government

led projects in Ethiopia. One of the unique characteristics of the program is that it has a variety

of large numbers of stakeholders with distinct job specifications. The AAHDPO project office

manages and administers the project as a client. Assisting AAHDPO in contract administration,

the consultants supervise and inspect the works. Micro and small scale enterprises (MSEs) are

responsible for the production of construction material and installation works. The contractors on

the other hand are responsible for the construction of major structures of the building with the

material provided to them by AAHDPO and MSEs. Since all frame structures of those buildings

are reinforced concrete, concrete production on those projects is practiced in significant amount.

On those projects, concrete is produced with crushed aggregate, sand, cement and water.

Crushed aggregates and cement is supplied by the AAHDPO and contractors supply sand due to

insufficient sand suppliers from one resource [26].

The quality of concrete produced on those projects varies from good to bad and the variability in

the quality of concrete production on those projects is due to lack of testing, selecting and

handling of concrete making materials[14]. The study further states that, lack of proper control

while producing concrete and poor workmanship also another factor which affects the quality of

those projects. Abebe (2005) also listed the above factors which are highly observed in Ethiopian

construction industry. He also further pointed that lack of understanding of the bulking effect of

sand, moisture content of aggregates and unknown dates of cement which might be expired

cements are another factor that might affect the quality of concrete produced but mostly omitted

in concrete construction of Ethiopia.

Hiwot (2012) also identified the key challenges in the construction industry of Ethiopia which

causes unsatisfactory quality for concrete construction. She mentioned unsatisfactory concrete

ingredients and steel reinforcement, poor workmanship and lack of adequate supervision. The

above studies agreed that there is a gap in the improvement of quality in overall building projects

of Ethiopia. Therefore, identifying the gap from accepted standard helps in the improvement of

quality of the construction sector.

The challenges with concrete production in Ethiopia are related to different factors which

contribute to overall quality production. Hence studying concrete production practices and

identifying the problems exist on projects helps to take corrective measures and protect those

public buildings from damage and to make them serviceable and durable. To enhance the quality


Addis Ababa University, AAiTPage xliii

of concrete on those public buildings, all stakeholders should work hard by implementing quality

management principles which can be applicable on concrete construction through quality

planning, quality assurance and quality control.

CHAPTER THREE

RESEARCH METHODOLOGY

3.1 IntroductionThis chapter discusses the research design and methodology used in acquiring the necessary

information to achieve the research objectives. It specifically presents the research design,

describes research approach and techniques, presents sampling techniques in terms of sample

size and selection, validity and reliability of the research, data collection methods and data

analysis methods.

3.2 Research strategy and typeThis is an assessment research with the aim of evaluating public building construction of Addis

Ababa Housing Development Projects in the context of concrete quality and its management

practices of constructing houses. It is emphasizing on examining the quality of concrete

produced on those projects on one hand and evaluating the existing management practice for the

improvement of concrete quality on the other hand.

3.3 Study designThe research uses both qualitative and quantitative data with the aim of evaluating the quality of

concrete used in currently undergoing projects of Addis Ababa Housing projects and the research

also tries to investigate the quality management practice for concrete by considering a case study

at Kuye Feche which is located at Addis Ababa, Akaki Sub city.


Addis Ababa University, AAiTPage xliv

3.4 Data collection methods and procedures

The research uses both primary and secondary data collection methods as a tool to gather the

necessary information. The primary data was collected using different methods and mainly

through in depth desk study, project site observation, interview with experts and concrete sample

test results. Secondary data was obtained from journals, codes of standards and other relevant

and related documents.

The study started by assessing different literatures that relates to the research. The literature

review acquired different data from journals, researches that has been made on related topics,

books, etc. Various standard codes for concrete such as Ethiopian Building code of standards

(EBCS), American Concrete institutes (ACI) codes and others have also been referred.

Desk study on selected projects was employed to assess the current concrete production practice

on those projects. The researcher also collected 44 lots (1 lot is 3 pieces of 15x15x15cm cube)

sample specimens based on ES ISO 1920-1:2014 and the specimens are cured based on ES ISO

1920-3:2014 and it was stored in molds for 24hours and after this period the specimens are

marked and removed from the molds and kept submerged in clear fresh water until taken out and

transported for test. Then the specimens are transported to Addis Ababa institute of Technology

laboratory (AAiT) for their compressive strength test to investigate the current quality status of

concrete produced in Addis Ababa housing projects using concrete statistical analysis methods.

A chart quality controlling method called Shewart chart is also used to determine the control

level of concrete production on these projects.

Rooted in literature review, observation and desk study, well organized closed interview

questionnaire was prepared and interviewed with 47 experts who are currently participating in

Addis Ababa Housing projects. The respondents are selected from the client (i.e. Addis Ababa

Housing Development Program Office, AAHDPO), consultants and contractors who are

involved in condominium housing projects, concerning their views and experiences related to

condominium housing projects.

Standard concrete quality management plan for those projects also prepared to assist the current

concrete production practice.


Addis Ababa University, AAiTPage xlv

Using all available data, interview and by applying statistical analysis method for compressive

test results obtained from the selected sample projects, detailed information about the work

environment characteristics, awareness and practice towards concrete production and its

management to enhance the quality of concrete produced on those projects is investigated.

Finally conclusion and recommendations are also drawn out based on the analyzed results and

discussions.

3.5 Sample size determination and sampling techniqueSample specimens for concrete from ongoing projects are collected from two selected big

projects that are found around Kuye Feche project area, which are named as Project 12 and

Project 17 which have 126 and 124 blocks, and 50 and 56 contractors respectively. These two

projects are selected based on the suggestion of authorized officials and experts working around

there. The main reason for selecting these projects is the availability of concrete work in

significant amount which helps to collect sample specimens and to investigate actual concrete

production practices from ongoing concrete production sites.

3.6 Ethical clearanceInitially support letter, which expresses the identity of researcher, is obtained from Addis Ababa

institute of Technology (AAiT). Then, for sample specimens, interview and data collection

procedures permissions was obtained from AAHDPO main office and then branch offices. All

the results of compressive strength are used only for research purpose to keep the good will of

the contractors who were cooperatives while the researcher takes sample specimen from their

corresponding site. Verbal consent was mandatory to obtain from every study subject before any

act.


Addis Ababa University, AAiTPage xlvi

CHAPTER FOUR

CONCRETE QUALITY MANAGEMENT PLAN FOR AAHDPOPROJECTS

4.1 IntroductionProject Quality Management Plan (QMP) is an essential document that any contractor or

consultant must have. It is the life line of a project that will ensure the end product that is going

to be delivered to client meet all the requirement and specifications. After studying the level of

quality management practice for concrete on those projects and believing that the preparation of

QMP helps in the improvement of quality of concrete, the author provides a proposed quality

management plan for concreting works in AAHDPO projects. The Quality Management Plan is

adapted and prepared based on different quality management plans used for international

projects.

The prepared project quality management plan for concreting activities (CQMP) document offers

essential information about concrete materials related to quality assurance (QA) and quality

control (QC) practices for Addis Ababa housing development project office (AAHDPO)

condominium building projects with much significant concrete structures. It is the author's

intention that, the document serves as a guide for developing a QMP for concrete construction of

significant concrete structures of AAHDPO projects.

The project management team, consultants and contractors should prepare and use QMP

documents (project-specific QC and QA procedures) which are appropriate and fits to a given

Project. Related to the scope of the research, the author limits the quality management plan to


Addis Ababa University, AAiTPage xlvii

only concreting activities where its implementation strongly helps in the improvement of

concrete production. Therefore it is the intention of this chapter to discuss the contents of the

prepared quality management plan documents where the full document is attached in the

appendix part of this thesis.

4.2 Organization of Concrete Quality Management PlanThe quality management plan is comprised of eleven sections which are discussed in depth in the

proposed quality management plan prepared. But it is the goal of this part of the thesis to outline

the contents that the document covers.

4.2.1. Introduction

This section describes the project setting, the contract and related documents and the quality

control plan overview. With project setting the owner of the project and other background of the

project which is related to Addis Ababa Housing project is discussed in brief. The quality

control plan overview briefly discuss the contractual relationships between client, contractors

and supervisors in assuring the quality of the current concrete production in Addis Ababa

Housing projects. It also outlines necessary checklists for storage of concrete materials, labor

enforcement and equipment proposals used in concrete production of those projects.

4.2.2. Project Quality Control Organization

This section of the document deals and presents the organization and key personnel involved in

the construction of Addis Ababa Housing projects to administer the projects such as Consultants

and contractors. Their responsibilities and authorities of each organization in the improvement of

concrete quality, the structure of the quality control organization with some suggested

modification and the minimum used and suggested training and experience of the quality control

officer and personnel.

4.2.3. Submittals

This section presents the procedures for processing submittal from contractors to consultants

then to client. It briefly suggest important procedures to be followed in using this submittal to

disseminate information among stakeholders which helps in good planning of resources used for


Addis Ababa University, AAiTPage xlviii

concrete production. It further suggested the approval and disapproval procedures that can be

applied in using these submittals.

4.2.4. Performance Monitoring Requirements

This section addresses quality control for performance monitoring requirements by following the

projects by using progress reports and updated schedule by the contractors. Quality control

reports which shall be conducted and the elements included in this reports are discussed and

progress reports regarding to overall project is also briefly described and some reporting formats

are suggested to encourage the use of this reports.

4.2.5. Inspection and Verification ActivitiesIn this section the quality control, verification, and acceptance testing plans is discussed in detail.

The plans will cover the type, test standard, frequency, control requirements, and assigned

responsibility for inspections and tests. For the verification purpose the consultant involvement

in relation to code of standards is also discussed. According to this plan the consultant’s resident

engineer will review and approve these plans as part of the contractor quality control plan

submittals and follows its accomplishment throughout the project life. Contractor's inspection

plan for testing and checklists which can be applicable in quality concrete production is also

presented in this section of the QMP.

4.2.6. Construction Deficiencies

This section provides the implemented procedures for tracking concrete construction deficiencies

(non-compliance and non-conformity) from identification of the non-compliance through

acceptable corrective action without compromising the quality of the concrete product. It defines

the prevention methods that can be applied in concrete production and how to identify or trace

existing problems and procedures to be followed in taking corrective action for deficiencies. It

also further states the controls related responsibilities and authorities for dealing with

noncompliant concrete products.

4.2.7. DocumentationThis section deals with reports which shall be documented in well-organized way to assess the

quality status of the project at any point. This documentation includes daily reports of concrete


Addis Ababa University, AAiTPage xlix

and other significant work items, testing and reporting forms which simplify keeping of

documents and any control of quality made at the project sites.

4.2.8. Field RevisionsThis part of the plan deals with changes or revisions that can be done based on actual site

condition which might be initiated by one of the stakeholders to improve the level of quality.

Section nine deals with the reporting standards of the final quality control to the client. Section

ten is all about the references made while preparing this proposed CQMP documents for use in

AAHDPO projects. Section eleven provides appendixes composed of sample forms for

qualification test schedule, inspection schedule, test schedule and typical construction forms. The

completed quality management plan with its appendices is attached as appendix in this thesis.


Addis Ababa University, AAiTPage l

CHAPTER FIVE

FINDINGS AND DISCUSSIONS

5.1 Introduction

This chapter consists of the research findings and discussions. The findings here are based on the

analysis of collected fieldwork data for compressive strength test results conducted on concrete

production sites and responses from experts through an organized interview questions.

A short description of general characteristics of the project and research respondents which

participated in interview is presented at the beginning for clear understanding of these findings

and analysis. Following this, statistical analysis based on compressive strength test result is done

and presented. Then, analysis of the data regarding to the research interview questionnaires, desk

study, and observations done at the studied sites is described. The analysis mainly deals with the

current cast in-situ concrete production practices in Addis Ababa housing projects and the

management practice to improve the current concrete quality to better level based on

observations and respondents opinion by comparing to the standards and scientific concrete

production practices. It also analyses the current concrete quality control level using one of the

control chart method known as Shewart control chart method by considering the obtained

compressive strength test results on those public projects as a quality measurement tool.

5.2 Project Description

5.2.1 The ProjectThe integrated housing development program is the one among mega and government led

projects in Ethiopia. One of the sole characteristics of the program is that it has a variety of large

numbers of stakeholders with distinct job specifications. The AAHDPO project office manages

and administers the project as a client. Assisting AAHDPO in contract administration, the

consultants’ supervise and inspect the works. Micro and small scale enterprises (MSEs) are also


Addis Ababa University, AAiTPage li

responsible for the production of construction materials and installation works. The contractors

on the other hand are responsible for the construction of major structures of the building with the

material provided to them by AAHDPO, MSEs, and themselves. Since all frame structures of the

program’s buildings are reinforced concrete, concrete production is practiced in significant

amount.

The selected projects are found in Kuye Feche housing project sites which are located in Akaki-

Kality subcity. Each project averagely consists of more than 6,500 housing units which will be

constructed with 53 contractors on average, and one consulting firm for each project. But

sometimes two consulting firms are assigned while the number of blocks becomes unmanageable

by one consulting firm which is decided and hired by AAHDPO.

5.2.2 Description of main project participants

5.2.2.1 AAHDPOAAHDPO is the responsible body for the administering and regulating the whole construction

and contract administration work. It is the one who hire and assign every consultant and

contractors to the site project offices. The project office on site is responsible for the follow up

and administration of the specific project site under the supervision of head office. It also follows

and controls whether the consultants and contractors are working according to the contract and

incase of problems occur, the project office takes corrective measures to improve the quality of

work. The respondents from those offices were nine engineers from different construction follow

up offices, which are located around Kuye Feche project sites.

5.2.2.2 ConsultantsThere are many different consulting firms in Kuye Feche site, whose consulting grade varies

from grade three to one, and are responsible for construction supervision and contract

administration of many blocks around the site. They are responsible for construction

management issues, such as works inspection, quality control and approval, material approval,

payment approval, and management of contractual issues. The respondents from the consultants

were 13, which had a high level of education and have work experience which varies from two to

more than eight years in construction projects of similar nature. Most of the resident engineers


Addis Ababa University, AAiTPage lii

working in the consulting firms have at least four years of experience and upwards of 12 years.

Some are also worked on other condominium projects since from the beginning.

5.2.2.3 ContractorsThe contractors are responsible for the construction of major structures of the building with the

material provided to them by AAHDPO, MSEs and themselves. The profile of the contractors

shows that most of contractors are educated or at least they have good working experience, and

have an average work experience of four years. There were 25 respondents from contractors

whose educational level varies from Diploma to BSc degree in different engineering and

interdisciplinary fields. The company profile of the majority of the contractors (65%) fall under

the category of GC/BC grade 5-6 and only a few (35%) were under category GC/BC grade 3-4.

The majority of the contractors or more than 95% of the respondents have only a foreman,

storekeeper, and security guard as key personnel. Whereas the contract document requests at

least a BSc holder engineer in civil engineering and other related fields who have at least four

years of experiences in related or the same project level. Respondents described that most of the

contractors have not participated in big projects before and some of them initially participate

only in condominium projects. However, currently there are few contractors that are participating

in other construction projects in addition to the condominium projects.

5.3 Personal background of respondentsTotally there were 47 respondents who participated and were interviewed to obtain necessary

data to strengthen the facts obtained from desk study, site observation and compressive strength

test results. Among the respondents, 9 of them (19.1%) are from client (i.e. AAHDPO), 13

(27.7%) are from the consultants, and the remaining 25 (53.2%) respondents are from

contractors. When we see their educational level, 6.4% have MSc degree, 72.3% of the

respondents have a BSc degree in civil engineering or other related fields, and the remaining

21.3% have a college diploma or certificate in building and concrete construction. Their

experience also varies highly and 55.3% of the respondents have an experience of zero to four

years, 29.8% of them an experience which varies from four to eight years, and the remaining

14.9% have an experience of more than eight years.


Addis Ababa University, AAiTPage liii

5.4 Statistical Quality Control of ConcreteStatistical Process (quality) Control is an analytical decision making tool which allows to see

when a production process is working correctly and when it is not. It is inevitable that variation

is present in any process. Hence, deciding when the variation is natural and when it needs

correction is the key to quality control. This control tool greatly helps in production process of

concrete by noticing variations and quality problems to enhance the production process of

concrete.

In concrete production, compressive strength tests are used as an immediate quality control tool.

Even if strength is a quality control tool in concrete production, the strength of concrete has an

inherent variability as it depends on the variations in properties of concrete and variations due to

testing methods. Therefore, proper care while taking test samples is crucial. The test samples

ought to be representative of the actual mass production, the testing method should follow the

right procedures which are specified in different codes of standards early from casting concretes

to specimen testing. If not, the compressive test results obtained from samples might be

deceptive and undependable.

Based on the objective of this thesis and understanding the level of importance of testing sample

specimens in assessing the quality of concrete, sample specimens which are casted from ongoing

concrete production sites of AAHDPO are collected and tested for their 28th day compressive

strength though some tests are done on 29th and 30th day of casting due to weekends.

In order to evaluate the quality of concrete used in Addis Ababa housing projects using statistical

quality control method, compliance and conformity criteria's found in the Ethiopian building

codes of standards (EBCS2:1995), ACI- 214 and ACI-318 have been used.

According to EBCS-2:1995, there are two compliance criteria's set as it has been discussed in

the literature review part of this thesis paper. As it is presented in the Ethiopian building code of

standards, the values of K1 and K2 are variable as shown in table 2.7. For this specific analysis of

test results, both the values of K1and K2 are taken to be 3MPa assuming that the lots considered

in all the projects are above the fifth lot. Among the two criteria's set, criterion 1 which is

applicable for small lots is used for this analysis.


Addis Ababa University, AAiTPage liv

While evaluating the compliance criteria's according to American standard cube results has been

converted to cylindrical strength using a conversion factor of 0.8 times cubic strength.

Mathematically it is expressed as,

fcyk= 0.8fcck.................................................................................................................... [Eq. 2.10]

Where, fcyk=Cylindrical strength and

fcck=Cubical strength

In order to proceed with the statistical analysis shown below, equations that have been presented

on this thesis are used for the determination of the mean, the standard deviation and the

coefficient of variation.

Table 5.1 Compressive Strength test results and analysis, according to EBCS-2 1995 and ACI-

318 of Project-12

Item No.

Com

pres

sive

Stre

ngth

(MP

a)

Mea

n(m

3 )

SD(N

/mm

2 ) fo

rC

ubic

Str

engt

h

SD(N

/mm

2 ) fo

rC

ylin

dric

alSt

reng

th

Coe

ffic

ient

of

Var

iati

on (

%)

Dec

isio

nA

ccor

ding

to

EB

CS-

2: 1

995

Dec

isio

nA

ccor

ding

toA

CI

318

Hs/Kf003

25.41

26.00 3.94 3.15 15.17Not

complied Complied

22.38

30.2

Hs/Kf004

42.54

37.97 6.11 4.89 16.09 Complied Complied

40.34

31.03

Hs/Kf006

36.52

29.87 6.07 4.86 20.33 Complied Complied24.61


Addis Ababa University, AAiTPage lv

Item No.

Com

pres

sive

Stre

ngth

(MP

a)

Mea

n(m

3 )

SD(N

/mm

2 ) fo

rC

ubic

Str

engt

h

SD(N

/mm

2 ) fo

rC

ylin

dric

alSt

reng

th

Coe

ffic

ient

of

Var

iati

on (

%)

Dec

isio

nA

ccor

ding

to

EB

CS-

2: 1

995

Dec

isio

nA

ccor

ding

toA

CI

318

28.49

Hs/Kf008

31.27


37.31

31.2

Hs/Kf011

28.89

22.96 6.12 4.89 26.65Not

compliedNot

complied

16.67

23.31

Hs/Kf014

31.45


38.72

26.54

Hs/Kf016

31.18


25.93

27.64

Hs/Kf017

32.18


28.95

31.47

Hs/Kf020

27.16

26.94 2.58 2.07 9.58Not

complied Complied

24.26

29.41

Hs/Kf023

30.0


29.54

27.72


Addis Ababa University, AAiTPage lvi

Item No.

Com

pres

sive

Stre

ngth

(MP

a)

Mea

n(m

3 )

SD(N

/mm

2 ) fo

rC

ubic

Str

engt

h

SD(N

/mm

2 ) fo

rC

ylin

dric

alSt

reng

th

Coe

ffic

ient

of

Var

iati

on (

%)

Dec

isio

nA

ccor

ding

to

EB

CS-

2: 1

995

Dec

isio

nA

ccor

ding

toA

CI

318

Hs/Kf025

36.1


28.82

31.19

Hs/Kf026

38.4


31.27

35.32

Hs/Kf029

22.7

21.24 3.78 3.03 17.80Not

compliedNot

complied

16.96

24.12

Hs/Kf030

28.85


31.29

26.91

Hs/Kf032

29.85


28.74

25.81

Hs/Kf034

36.03


29.92

30.52

Hs/Kf036

19.64

22.82 3.29 2.63 14.42Not

compliedNot

complied

26.21

22.6

Hs/Kf040 28.32 29.46 4.50 3.60 15.29 Complied Complied


Addis Ababa University, AAiTPage lvii

Item No.

Com

pres

sive

Stre

ngth

(MP

a)

Mea

n(m

3 )

SD(N

/mm

2 ) fo

rC

ubic

Str

engt

h

SD(N

/mm

2 ) fo

rC

ylin

dric

alSt

reng

th

Coe

ffic

ient

of

Var

iati

on (

%)

Dec

isio

nA

ccor

ding

to

EB

CS-

2: 1

995

Dec

isio

nA

ccor

ding

toA

CI

318

34.42

25.63

Hs/Kf041

19.30

23.27 4.22 3.38 18.13Not

compliedNot

Complied

22.8

27.70

Hs/Kf044

30.10

24.70 5.64 4.51 22.83Not

compliedNot

complied

18.85

25.15

Table 5.1.a. Summary of compliance and conformity from table 5.1

Items

Compliance Accordingto Ethiopian Standards

EBCS-2:1995

ComplianceAccording to

ACI 318Number % Number %

Defective lots 7 35.0% 5 25.0%

Non Defective lots 13 65.0% 15 75.0%

On this project 20 Lots of concrete which brings 60 pieces of total sample specimens are

collected from different 20 contractors with a specified characteristics strength of 25MPa (C-25).

Based on compliance criteria's of Ethiopian standards (EBCS-2:1995) and as shown in table

5.1.a, 35% of the lots found to be defective whereas 65% of samples are non-defective and

satisfies the specified requirement by the client. The same lots evaluated according to ACI 318

shows that, the number of defective lots goes down to 25% and the number of lots of non-

defective goes to 75%.


Addis Ababa University, AAiTPage lviii

All tests are conducted from ongoing concrete work of slabs, beams and columns and most of

them are accepted by the consultants as they are. Therefore, non-destructive test shall be

conducted on those non complying concrete structures.

The level of concrete quality control also investigated according to ACI-214. In this standard the

level of control has been stated and classified based on coefficient of variation and standard

deviation from excellent to poor. Tables 5.2.a and 5.2.b below summarizes the status of control

on this project based on the results standard deviation and coefficient of variation respectively.

Table 5.2.a Level of control based on Standard Deviation (ACI-214)

Level of control Based on (SD) Number of lots Percentage (%)Excellent (<2.8) 8 40.0%

Very good (2.8-3.4) 6 30.0%Good (3.4-4.1) 1 5.0%Fair (4.1-4.8) 1 5.0%Poor (>4.8) 4 20.0%

Table 5.2.b. Level of control based on Coefficient of variation (ACI-214)

Level of control Based on(coefficient of Variation) Number of lots Percentage (%)

Excellent (<7) 2 10.0%

Very good (7-9) 2 10.0%

Good (9-11) 5 25.0%

Fair (11-14) 1 5.0%

Poor (>14) 10 50.0%

As it is shown on the tables 5.2.a and b above, the level of control varies greatly from poor to

excellent within a project. Though the project is supervised by one consulting firm with 50

different contractors whose grade varies from five to three, the analysis reveals that, greater

variations and non-conformity is available even within a project. Therefore, the level of

supervision needs improvement for better concrete production on those projects. From

observation and contract document it can be understand that, the number and experience of

consultant’s personnel for each project is not sufficient to administer and control the overall

quality of the project. Hence number of supervision consultants or their personnel shall be


Addis Ababa University, AAiTPage lix

increased to address better level of control and improve the quality. Further observation on

investigated sites by the author shows that poor quality controlling is observed in many buildings

of Addis Ababa housing projects.

Besides ACI-214 which helps in determining the level of control in concrete production, the

author also used Shewart chart to assess the level of quality control in concrete production. This

chart method is useful in quality control of a production process. The Shewhart chart will have a

horizontal central line which represents the expected mean value of the test results on the

samples taken from production; in the case of concrete, the Target Mean Strength (TMS) for a

chart controlling compressive strength. Lines representing the upper control limit (UCL) lower

control limit (LCL), upper warning limit (UWL) and lower warning limit (LWL) may also be

added. Generally action is required if a result is beyond either of the control limits.

Figure 5.1 below shows the level of control and pattern of production on this project.

Figure 5.1 Control of concrete production of Project 12 using Shewart chart method

According to Shewart chart, 50% of tests shall be above targeted mean strength and the rest 50%

falls below the targeted mean strength but within the control limits. The chart for project 12

shown on figure 5.1 indicate that, 21.67% of test results are below the lower warning limit

(LWL) which indicates actions must be taken to enhance the level of quality of concrete

production process and 3.33% of test results fall below the lower control limit which is rare to

0

10

20

30

40

50

60

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59

Com

pres

sive

Str

engt

h R

esul

ts (N

/mm

2)

Test Results UCL LCL UWL LWL Specified Strength(fck) TMS

Test samples number


Addis Ababa University, AAiTPage lx

happen in quality concrete production. This chart which is essential in noticing poor quality

production process in concrete shows comparable result with compliance criteria's provided by

EBCS and ACI code of standards as discussed above. In addition to this, both the consultant and

contractor are responsible for any quality problems exist on those projects. Therefore, the

production process and control level of concrete on this project should be improved by taking

different correction measures related to the concrete making materials, the production process

and workmanship

The second investigated project found around Kuye Feche site is named as Project 17. The brief

presentation of test data and analysis of the results are discussed in subsequent pages.

Table 5.3 Compressive Strength test results and analysis, according to EBCS-2 1995 and ACI-

318 of Project 17

ItemNo.

Com

pres

sive

stre

ngth

(MP

a)

Mea

n(m

3 )

SD (

N/m

m2 )

for

cubi

c St

reng

th

SD (

N/m

m2 )

for

Cyl

indr

ical

Str

engt

h

Coe

ffic

ient

of

vari

atio

n (%

)

Dec

isio

n A

ccor

ding

to E

BC

S-2:

1995

Dec

isio

n A

ccor

ding

to A

CI

318

Hs/Kf001

41.23

35.73 5.37 4.30 15.03 Complied Complied30.5

35.46

Hs/Kf002

33.1


30.63

25.7

Hs/Kf005

19.84

22.21 6.41 5.13 28.85Not

compliedNot

complied29.4617.32

Hs/Kf007

31.2

31.85 6.04 4.83 18.95 Complied Complied38.1826.16

Hs/Kf009

40.94


Hs/Kf010

19.37

20.78 4.01 3.21 19.30Not

compliedNot

complied17.6725.31

Hs/Kf012 26.38 25.04 1.39 1.11 5.54 Not Complied


Addis Ababa University, AAiTPage lxi

ItemNo.

Com

pres

sive

stre

ngth

(MP

a)

Mea

n(m

3 )

SD (

N/m

m2 )

for

cubi

c St

reng

th

SD (

N/m

m2 )

for

Cyl

indr

ical

Str

engt

h

Coe

ffic

ient

of

vari

atio

n (%

)

Dec

isio

n A

ccor

ding

to E

BC

S-2:

1995

Dec

isio

n A

ccor

ding

to A

CI

318

23.61 Complied

25.14

Hs/Kf013

30.24


Hs/Kf015

22.8

25.23 3.11 2.49 12.32Not

Complied Complied28.7324.15

Hs/Kf018

36.32


Hs/Kf019

31.07


Hs/Kf021

19.67

20.43 2.94 2.35 14.39Not

CompliedNot

Complied17.9523.68

Hs/Kf022

38.1


Hs/Kf024

19.8

24.51 4.39 3.51 17.90Not

CompliedNot

Complied28.4125.35

Hs/Kf027

18.6

23.39 4.44 3.55 18.98Not

compliedNot

complied27.4

24.15

Hs/Kf028

40.3


Hs/Kf031

18.25

20.60 5.47 4.38 26.56Not

compliedNot

complied16.6926.85

Hs/Kf033

32.7632.37 4.91 3.93 15.17 Complied Complied27.28


Addis Ababa University, AAiTPage lxii

ItemNo.

Com

pres

sive

stre

ngth

(MP

a)

Mea

n(m

3 )

SD (

N/m

m2 )

for

cubi

c St

reng

th

SD (

N/m

m2 )

for

Cyl

indr

ical

Str

engt

h

Coe

ffic

ient

of

vari

atio

n (%

)

Dec

isio

n A

ccor

ding

to E

BC

S-2:

1995

Dec

isio

n A

ccor

ding

to A

CI

318

37.08

Hs/Kf035

27.53

21.86 5.35 4.28 24.49Not

CompliedNot

Complied21.17

16.9

Hs/Kf037

20.5

25.53 6.01 4.81 23.54Not

Complied Complied32.2

23.85

Hs/Kf038

28.4


Hs/Kf039

31.35

25.00 6.28 5.02 25.12Not

CompliedNot

Complied24.8618.79

Hs/Kf042

31.65


Hs/Kf043

41.42


31.54

28.69

Table 5.3.a. Summary of compliance and conformity from table 5.3

Items

Compliance According toEthiopian Standards

EBCS-2:1995Compliance According to

ACI 318

Number % Number %

Defective lots 11 45.8% 9 37.5%

Non Defective lots 13 54.2% 15 62.5%


Addis Ababa University, AAiTPage lxiii

On this project, 24 Lots of concrete which brings 72 pieces of total sample specimens are

collected from different 24 contractors. According to the test results based on compliance

criteria's of Ethiopian standards (EBCS-2:1995) and as shown in table 5.3.a, 45.8% of the lots

found to be defective whereas 54.2% of samples are non-defective and satisfies the specified

requirement by the client. The same lots have been evaluated according to ACI 318 and the

result shows that, the number of defective lots goes down to 37.5% and the number of lots of

non-defective goes to 62.5%.

All sample specimen tests for compressive strength are conducted by the author at Addis Ababa

Institute of Technology (AAiT) with samples collected from ongoing concrete work of slabs,

beams and columns of Addis Ababa housing projects and most of them are accepted by the

consultants as they are. These results show that, as there is a gap in concrete production practice

and the level of control by the consultants. Therefore, nondestructive test shall be conducted on

those non complying concrete structures.

The level of concrete quality control is also investigated according to ACI-214. In this standard

the level of control has been stated and classified based on coefficient of variation and standard

deviation from excellent to poor as discussed in the literature review part of this thesis.

Tables 5.4.a and 5.4.b below summarizes the status of control on this project based on the test

results standard deviation and coefficient of variation respectively.

Table 5.4.a. Level of control based on Standard Deviation (ACI-214)

Level of control Based on(STD) Number of lots Percentage (%)

Excellent (<2.8) 5 20.8%

Very good (2.8-3.4) 3 12.5%

Good (3.4-4.1) 5 20.8%

Fair (4.1-4.8) 3 12.5%


Addis Ababa University, AAiTPage lxiv

Poor (>4.8) 8 33.3%

Table 5.4.b. Level of control based on coefficient of variation (ACI-214)

Level of control based on(coefficient of Variation) Number of lots Percentage (%)

Excellent (<7) 2 8.3%

Very good (7-9) 0 0.0%

Good (9-11) 1 4.2%

Fair (11-14) 3 12.5%

Poor (>14) 18 75.0%

As it shown above on the tables, the level of control varies greatly from poor to excellent within

a project. This project is supervised by one consulting firm with 56 contractors whose grade

varies from five to three. As it can be observed from tables 5.4a and 5.4.b above the level of

control on those projects varies significantly. According to ACI-214, 33% of test results based on

standard deviation and 75% of them based on coefficient of variation falls under poor category

of quality control. This indicates that the quality of concrete produced and the control level by

the direct stakeholders (i.e. client, consultant and contractor) is poor and improvement on this

area is mandatory. Since this buildings are public projects where many people live together, the

buildings shall constructed with only a quality concrete which will have good strength and

durability.

This project is also evaluated with the use of Shewart chart to analyze the quality of the

production process. Figure 5.2 below shows the presentation and evaluation of test results using

Shewart chart.


Addis Ababa University, AAiTPage lxv

Figure 5.2 Control of concrete production of Project B using Shewart chart method

According to the chart above, 19.44% of the test results are below the lower warning limit which

indicates that, action shall be taken in concrete production to improve the quality of the produced

concrete whereas about 31.9% below the specified strength. This indicates corrective measures

and strong level of control shall be implemented in order to improve the current level of

concrete.

Generally, tests conducted on both projects shows the gap in concrete quality and also the level

of control in the production process. Consultants who participate in the supervision work needs

to work hard in controlling the quality of concrete. Not only consultants but also all stakeholders

should implement proper quality management for concrete production and the need for

management commitment is also mandatory.

5.5 Comparison between Project 12 and Project 17Based on the data obtained from test results and analysis made on preceding sections both the

projects shows a significant number of non-compliance with both Ethiopian Standards (EBCS-

2:1995) and ACI-318. According to the test results conducted 35% and 45.8% of the tests of

project 12 and 17 respectively found to be defective based on EBCS-2:1995 and 25% of project

0

10

20

30

40

50

60

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71

Com

pres

sive

Str

engt

h (N

/mm

2)

Test Samples UCL LCL UWL LWL specified strength (fck) TMS

Test Sample numbers


Addis Ababa University, AAiTPage lxvi

12 and 37.5% of project 17 are also found to be defective based on ACI-318 compliance and

conformity criteria's. But it has been observed that those structures are accepted as they are with

another test samples which are conducted by contractors. Interview with some experts who are

involved in these projects posited that, it is common practice to prepare another good sample for

test by washing sand and increasing the cement content of the mix which might improve the test

result which is unrepresentative of the actual grade and quality of concrete casted on job site.

This practice shall be avoided by proper supervision and control while taking sample test

specimens to obtain a representative sample result of the structures of the buildings.

The level of control on both projects also investigated in preceding topics based on ACI-214

using their standard deviation and coefficient of variations. According to the result obtained,

20% of the test results in project 12 fall in poor level of control category while project 17 have

33% of poor level of control based on their standard deviations. When we compare the projects

based on their coefficient of variation, 50% of test results of project12 and 75% test results of

project 17 falls in poor category. This indicates that, the level of control in concrete production

of those projects have a problem. Therefore, care shall be given to proper quality control and

assurance of concrete structures of these public buildings.

As it has been showed in the above analysis and discussions the quality of concrete production

varies greatly from poor to excellent. However, numbers of poor and defective test results are

noticed in significant amount which needs production improvement and better quality control

and assurance.

Observation shows that, in order to improve the quality of concrete the client uses OPC which

have higher strength grade than PPC cement amounting about 360Kg/m3. Ethiopian Standard

ES1177-1:2005 specifies class 32.5 for PPC whose standard strength is between 32.5MPa and

42.5MPa and class 42.5 usually OPC with standard strength of between 42.5MPa and 52.5MPa.

Hence, using OPC means that higher strength cement is in use for those projects to produce only

a C-25 concrete with specified characteristics strength of 25MPa. This shows that the cost of

achieving concrete quality due to the cement used is found in significant amount. Another cost is

related to supervision cost which is paid for consultants to assure the quality of the overall

projects. Even if with all these cement content and consultants who supervise and control quality

are found, compressive strength tests conducted on the investigated projects shows that, poor and


Addis Ababa University, AAiTPage lxvii

non-complied concrete is found in significant amount. Therefore, more efforts of all stakeholders

are mandatory to enhance the level of quality of concrete production.

5.6 Quality Concrete Production PracticesThe quality of a finished concrete structure is highly affected by different major factors which

strongly affects the overall concrete quality. The first part is related to concrete materials which

include selection, handling and storage of concrete making materials. The second part includes

the production processes employed to concrete such as batching, mixing, transporting, placing

compacting, finishing and curing. The quality of the freshly mixed and hardened concrete is

affected by all the above factors. Beside those listed factors, the standard of workmanship in

handling, batching, mixing, compacting, finishing, and curing of the concrete greatly affects the

overall concrete quality. The standard of workmanship throughout the concreting operations is

therefore extremely important in construction of a good quality concrete structure.

Unfortunately, although materials are regularly checked, monitored and tested, the workmanship

which is harder to specify and quantify is often given little attention or ignored completely.

Hence, the subsequent part of this thesis paper discusses and interprets the data obtained from

site observations, desk study, interviews, and compressive strength test results regarding to

concrete materials and its production process to investigate the level of site concrete production

and the quality management practice in Addis Ababa housing projects.

5.6.1 Quality of Concrete making materialsConcrete is a composite material which consists a binding medium within which are embedded

particles or fragments of relatively inert mineral fillers. It is commonly produced from cement,

aggregates (coarse and fine), water, and sometimes admixtures are used when some important

behavior is needed. Since, it is a composite material and composed of the above listed

ingredients, the overall concrete quality produced at site is affected by the property of each

ingredient. Therefore, proper selection based on test results, handling and storage of those

ingredients strongly helps to improve the quality of concrete. The actual concrete making

materials used in concrete production of Addis Ababa Housing projects and their level of quality

investigated from site observation and interview is briefly discussed in the next subtopics.


Addis Ababa University, AAiTPage lxviii

5.6.1.1 Portland CementCement is a material with adhesive and cohesive properties which make it capable of bonding

mineral fragments into a hard continuous compact mass. When it is mixed with water it forms a

paste to create strong bond between fillers. Hence, the qualities of this material have a great role

in producing concrete.

There are two types of Portland cements which are used in Addis Ababa Housing projects

supplied from different suppliers in the country. These cements are ordinary Portland cement

(OPC) and Portland pozzolana cement (PPC) which is supplied from Derba, Dangote, National,

Messobo, Muger, East and other cement factories which are the reliable sources of the project.

Ordinary Portland cement is the most common cement used in general concrete construction

when there is no exposure to sulfates in the soil or in ground water. Portland Pozzolana cement

(PPC) is manufactured by the intergrinding of OPC clinker with 10 to 30 percent of pozzolanic

material [2].

The use of PPC in concrete construction has an economical advantage over OPC due to an

expensive clinker is substituted with 10 to 30 percent pozzolanic material. Although the use of

PPC in terms of economy is more advantageous, a wide use of OPC for concrete production is

observed in all Addis Ababa Housing projects. This contradicts with the concept of low cost

housing advantages that can be obtained in terms of concrete production of those public

buildings by using PPC.

It has been observed that, in all projects they use C-25 concrete for most concrete structures

where the contract document and specification specifies a minimum cement content of

360kg/m3. Experiences show that, currently it is possible to produce a C-25 concrete by using

280Kg/m3 to 320Kg/m3 (EEPCO project, Akaki Substation is good example which used

320Kg/m3 to produce a C-25 concrete). On contrary, the use of cement in Addis Ababa Housing

seems a little overstated because the specification which is part of the contract document

specifies the use of minimum cement for C-25 is 360Kg/m3and all contractors are struggling to

produce the specified strength with allowed cement content. An interview with experts show that

they agree the use of overload cement is there in the production of concrete but they associate the

problem with quality issue. Even though there is an excess use of cement in producing C-25

concrete, the excess part of cement may help to improve the poor quality of concrete that arises


Addis Ababa University, AAiTPage lxix

from material quality and concrete production process. But still it misses the concept of low cost

housing by increasing the cost of concrete on the projects due to the use of OPC rather than PPC

which is cheaper and able to achieve equivalent strength at 28th day.

Observations and the responses from interviewed respondents show that no cement test is

conducted on job site or at a branch office level. The cement is supplied by the client

(AAHDPO) and main office is responsible for distributing and testing of the procured cement.

Cement test results and certification of the cement production factories based on ES 1177-1:2005

by Ethiopian Conformity Assessment Enterprise (ECAE) is the only references they have. But

further sample tests should be conducted when it is necessary, for approval in using cement

because its properties might be affected due to storage, weather and age of cements.

Cement absorbs moisture readily from air as briefly discussed on the literature review part of this

research. Hence, it is essential to protect it from dampness before it is used, so that it may fulfill

its intended functions. It has been observed that, big cement warehouses constructed from

corrugated iron sheets are the place where cement is stacked for each project which is

transported from cement factories. Earlier than two or three days when concrete work is done by

contractors, all the contractors took their loads of cement into their temporary stores.

The cement bags procured in 50 Kg bags are stacked on a temporary timber platform in big

warehouses constructed at project sites, as observed. Interview from one of the project

storekeeper who keeps cement tells that, always cements which come first will be used first but

the researcher reliably gathered in one of the stores that the latest bag of cement was stacked on

top of the existing ones. Even it is difficult to know that which cement is the oldest and which

one is the new produced cement as the production date is not specified. On site, they only follow

first in first out (FIFO) concept but it doesn't guarantee about the age of cement because cements

may be stored for longer time due to financial problems and delays on those projects.

It has been discussed on the literature review part of this thesis that cement which is 4 months

old and above should be classified as "aged" and vital cement tests should be rechecked for

concrete production to fulfill their intended functions. It also known that, even when we store

cement under good conditions, bagged cement may lose 20 percent of its strength after 2 months

of storage, and 40 percent after 6 months of storage. Hence, proper care shall be given to storage


Addis Ababa University, AAiTPage lxx

of cement. As a result, Ethiopian Standards Agency (ESA) should oblige the producers to stamp

the production date of cements produced in the country. This may help to identify the aged

cement with the new one and to undergo any necessary rechecking of cements by using

appropriate test methods.

5.6.1.2 AggregatesApproximately three-quarters or 60-75% of the volume of conventional concrete is occupied by

aggregates. Considering the volume it can be comprehend that, as they are one of the main

important constituents in concrete production and give body to the concrete, reduce shrinkage

and affect economy. It is predictable that a constituent occupying such a large percentage of the

mass should contribute important properties to both the fresh and hardened state of the product.

Therefore, aggregates used for concrete shall be better quality to achieve the intended concrete

quality and also needs proper production, storage and handling.

There are two types of aggregates used in Addis Ababa Housing projects which are crushed

aggregates as a coarse aggregate and sands from river deposits as fine aggregates. The coarse

aggregates are crushed aggregates which are supplied by the AAHDPO after procuring from the

nearest quarry in Addis Ababa. Fine aggregates or sand is supplied by the contractors and

procure it from different sources. The most common sources of sands are from Meki, Langano,

Koka, Metehara, Lafesa, Sodere and Minjar. Almost all respondents agreed that, there is a big

problem in getting good sand for production of concrete due to different reasons. The first is

related to lack of automated and reliable suppliers for sand, most of them works manually using

human power. Another reason is related shortage to river sand near Addis Ababa which leads to

search fine aggregates from a distant area. Searching cheap sand by the contractors for concrete

also brings the use of poor quality sands in concrete production of Addis Ababa Housing

Projects.

Since aggregates used on those public projects are bought from different quarry sites or river

deposits, the mineralogical contents of aggregate shall be tested. Standards and specifications

also require certain properties of aggregate to be tested to accept the using of aggregate in the

concrete mixes. Other properties can be required for calculating concrete mix proportions.


Addis Ababa University, AAiTPage lxxi

Even if it is known that, different conformity tests shall be conducted on aggregates used for

concrete that are discussed on literature review part of this paper, only a visual test and jar test

for fine aggregates are employed. According to the observation made and interview with experts,

tests for coarse aggregates is conducted only when the material is procured by the client from the

suppliers and within one procurement contract from 5,000m3 to 10,000m3 of aggregates is

purchased based on the demand of each projects. The tests for aggregates are conducted based on

compulsory Ethiopian Standard, CES23:2015, but no regular controlling mechanisms of those

ingredients are employed yet.

Regarding to fine aggregates, the most frequent test done on site is only by visual inspection but

some of interviewed respondents pointed that, in case of indistinctness the use of jar test is

employed to know the level of silt content and sand which consists more than 6% silt is rejected

from the use in concrete production. The author observed that, sands with too much of silt

content is observed in many places even in the site. The photo below shows some damped sands

ready for concrete production.

(a) (b)

Figure 5.3. Dumped fine aggregate (Sand) for concrete production with much silt and dusts

As it is shown in Figure 5.3 (a) and (b), sands with too much silt content and dust that can be

easily identified by visual inspection is damped and used in concrete production of those

projects. Consultants who are responsible for quality control are accepting those materials as an

ingredient for concrete, which shows the level of control in quality of concrete materials is poor.


Addis Ababa University, AAiTPage lxxii

The shape, size and texture of aggregates greatly affect the workability of concrete due to the

differences in surface lubrication of those aggregates which are caused by different shapes and

sizes. It has been observed that, the shapes and sizes of the aggregates vary highly in most of

visited damping areas. Even very fine aggregates have been observed with larger sizes of

aggregates which will affect the overall properties of concrete like workability, strength and

durability.

(a) (b)

Figure 5.4. Coarse aggregates for concrete with poor gradation

Figure 5.4 (a) and (b) shows the actual coarse aggregate gradation in use for concrete production

on those public projects which mainly influences the space filling and packing of concrete

structures that helps to produce a good strength and durable concrete. The figure clearly shows

the particle distribution in those aggregates varies in significant amount. Even the gradation

varies greatly from one source to another source which is used to produce the same grade of

concrete with the same mix design. Hence, proper quality control and quality assurance on these

materials is very crucial to obtain a good quality concrete product.

Interview with respondents also strengthen the observation by the author and they all agree that,

poor gradation of coarse aggregates exists on these projects in significant extent and basically

two causes of poor gradation are listed by them. The first is related poor capability of the

crushers used at quarry and lack of financial power of the manufacturers to provide automated


Addis Ababa University, AAiTPage lxxiii

crushers which helps in eliminating poor aggregate gradations. The second reason is related to

stockpiling of those aggregates on site which is degraded by weather when it is stored for longer

period of time and loaders and dump trucks are also moving on it while loading and unloading of

these aggregates at production sites.

Concrete aggregates should be free from impurities and deleterious substances which are likely

to interfere with the process of hydration, prevention of effective bond between the aggregates

and matrix. The impurities may also reduce the durability of the aggregate. Apart from the tests,

shapes, sizes and other properties of aggregates which should be considered in production of a

quality concrete, the way they stockpile aggregates on site greatly affects the overall concrete

production. It has been observed that the stockpiling areas for aggregates are not good because it

is just soil ground without any protection under it. This allows the silts, clays and other organic

impurities found on the ground going to be mixed with other concrete ingredients and affects the

properties of the produced concrete. Hence care should be given to those aggregates in the

production, stockpiling and testing which give the most important concrete properties such as

strength, durability, shape and economy of the final product.

5.6.1.3 Water used for Concrete ProductionWater is one of the most important ingredients of concrete which plays a great role in concrete

production. Generally it is agreed that, water which is used for drinking is safe to use in concrete

production. If water is properly designed in concrete mixture, it will possess the desired

workability for fresh concrete and the required durability and strength for hardened concrete.

Since it helps to form the strength giving cement gel, the quantity and quality of water is required

to be looked into very carefully.

Drinkable ground water which is distributed for Akaki area residents is used in the production of

concrete in all investigated projects of Addis Ababa Housing projects around Kuye Feche. The

water used for concrete production is supplied by the client Addis Ababa project office using

water trucks for transportation from the source. This transported water is distributed for all

contractors who participate on those public projects. Respondents tell that, no tests are conducted

for water used in concrete production. All respondents agreed that, since the water is safe to

drink it is a good water to use for concrete.


Addis Ababa University, AAiTPage lxxiv

Each contractor has its own water tanker constructed underground with concrete bottom slab and

hollow section concrete blocks (HCB) plastered internally. The top part is open and has no

covering slab or other material.

Figure 5.5 Water tankers with impurities from the surrounding sites

Even if it is good to have water tanks to avoid the water shortage in concrete production, dusts

and impurities from surroundings are there on most of the investigated projects. Figure 5.5 also

shows the way water is stored in most projects for concrete and the level of cleanness of the

water stored. As it can be seen from the figure, the water has impurities which come into the tank

from the job sites and surrounding. Therefore, covering the top of the water tanker may help in

protecting the water from dusts, wastes and other impurities not to enter. Respondents also

suggested that cleaning the water tanker may help in order to get clean water which is not

affected by dusts and other impurities.

5.6.2. Concrete ProductionProduction of quality concrete requires methodical care exercised at every stage of manufacture

of concrete. It is interesting to note that the ingredients of good concrete and bad concrete may or

may not be the same. If proper care is not exercised and good rules to produce concrete are not


Addis Ababa University, AAiTPage lxxv

observed, the resultant concrete is going to be of poor quality which doesn't satisfy the required

purpose.

Freshly mixed concrete quality is influenced by its constituent materials, procedures of

production, and equipment used. To obtain a good quality concrete structure, attention should be

paid to all aspects of concreting operations. The quality of concrete does not only depend on the

quality and uniformity of the concrete discharged from the mixer, but also on the skill and

knowledge shown on the site in carrying out the various operations including batching, mixing,

transporting and placing, compacting, finishing, and curing the concrete. A high standard of site

workmanship is required to produce a high standard of concrete work and much depends on the

skill and expertise of the supervision engineers, foreman and skilled and semi-skilled laborers. It

is also undeniable that, with simple highly repetitive work good quality can still be achieved with

less highly skilled labor.

The various ingredients of concrete and their current practice in investigated projects of Addis

Ababa housing has been discussed above. The succeeding part of this paper briefly discusses and

evaluates the current concrete production process i.e. batching, mixing, transporting and placing,

compacting, finishing, and curing of concrete which practiced on those public projects.

5.6.2.1 Batching of ConcreteBatching involves measuring the quantities of the concrete making materials (cement, water,

sand, and coarse aggregate, and sometimes admixtures). The correct amount of each material

must be batched if the quality of the concrete is to be maintained in both individual and

successive batches. Mistake in measuring the ingredients reduces the accuracy of the batching.

Poor accuracy in the batching cause’s variation in the properties and the quality of the concrete

produced.

Even if it is advisable to use weight batching to reduce variations related to batching and in order

to get improved quality of concrete, volumetric onsite batching is commonly used in all observed

sites of Addis Ababa housing projects. This method is used due to easiness in measuring the

quantities of ingredients for manual concrete production. As it has been discussed above, C-25

is the frequent concrete grade used for all types of buildings commonly G+4 and G+7. A box

internal size of 50x40x18cm (length, width and depth respectively) is used to measure sand and


Addis Ababa University, AAiTPage lxxvi

coarse aggregates used. Whereas cement which usually used ordinary Portland cement (OPC) is

measured per bag where each bag weighs 50Kg and the water is measured by liters. The mix

ratio used to produce a C-25 concrete in all projects is 1:2:3 which represents one bag cement

(50kg), two boxes of sand and three boxes of coarse aggregates respectively and they usually

uses 350 liters diesel mixer.

All of the respondents replied that no adjustment of bulking sand effect and absorption capacity

of aggregates are considered. It has been observed that no water measurement for each mix is

taken; the operators only balance the water by using trial and error method and they use their

experienced judgment. This greatly affects the water cement ratio (w/c) and workability of the

concrete. Hence, this problem adversely affects the compressive strength of concrete because w/c

ratio is inversely proportional to strength of concrete; high water cement ratio refers to low

compressive strength of concrete.

Two common problems of batching are observed and also listed out by respondents in concrete

production of those project sites. These problems generally can be grouped into two; over

batching and under batching. Over batching is observed related to the box where excess sand and

aggregates are batched and additional sand or aggregates may be used due to lack of proper

counting for each mix. This may leads in great variation of concrete mix and affects the overall

concrete quality. The second common and major problem that creates higher variation in

concrete batching is called under batching which refers to lack of the expected specified

ingredient in each mix. This situation usually happened when they batch the ingredients, they

may forget the added and remaining batch of each ingredient into the mixer as a result, a box of

sand or aggregate may be missed. Another cause may be related to the materials thrown out of

the box may not fully added to the mixer drum and fall on to the ground and this brings shortage

in one mix and excess materials on the other mix which leads to greater variation in the quality

of concrete.


Addis Ababa University, AAiTPage lxxvii

(a) (b)

Figure 5.6. Common problems of batching

Figure 5.6 of above shows, the two common problems of batching usually called over batching

and under batching. Figure 5.6.a clearly shows when aggregates are over batched from their

provided box size which leads to a greater variation in concrete quality. Figure 5.6.b shows one

of the reasons for under batching that may happen due to the use of smaller or broken boxes for

the batching of concrete.

(c) (d)

Figure 5.6.Common problems of batching

Figure 5.6.c and d shows another common problem which leads to over batching or under

batching of ingredients. As it can be seen in the figures above sand and aggregates are not


Addis Ababa University, AAiTPage lxxviii

dumped in proper and separate location. This leads to the materials to be mixed each other and as

it can be seen from the picture, the labors are measuring a sand and aggregate mix as an

aggregate. This brings a deficiency in one material and a surplus in the other material that

directly contradict with the mix design which leads to poor concrete batching and finally poor

concrete product.

Discussion with experts regarding to the above problems observed in concrete batching shows

that, consultant's site inspector and the resident engineers tries to control the uniformity of

batching but it is always not simple and true to follow each progress of batching. This is related

to insufficient staffs by the consultants to control each and every stages of work. Therefore

training and serious control of workmanship regarding to batching and other concrete production

processes is mandatory by both contractor's and consultant's experts.

5.6.2.2 Mixing of concreteOnce we have batched the correct amount of materials into the mixer, thorough mixing is crucial

for the production of uniform quality concrete with smaller variation. Thorough mixing means

distributing the concrete ingredients uniformly and spreading the cement-water paste evenly onto

the surfaces of the aggregates. If this is not achieved, the quality of the concrete discharged will

not be the same throughout the mix hence high degree of variations in the mixes that leads to

poor quality of concrete may be obtained.

Mixing of concrete in all observed sites is done with mixers usually by using 360 liters mixers

which produces only one mix at a time (usually 1:2:3). Though respondents from all stakeholders

replied that, the mixing time affects the mix of concrete, it has been given little attention to all

factors that affect uniform mixing. Most of the respondents agreed that attention to mixing shall

be given in mixing of concrete especially related to mixing time. Mixing shall be done for only

sufficient time, if mixing takes place for over a long period, evaporation of water from the mix

can occur, with a consequent decrease in workability and an increase in strength. Another effect

is that of grinding of the aggregates, particularly if soft, the grading thus becomes finer and the

workability lower.

As it has been observed in actual concrete production sites, no one controls the mixing time and

procedures, the mixer operators who do not understand the effect of mixing time on the quality


Addis Ababa University, AAiTPage lxxix

of concrete uses their judgment on mixing time. Therefore, all stakeholders who participate in

concrete production of Addis Ababa housing shall give attention to concrete mixing. Consultants

are always there to control the quality of concrete but lack of proper supervision of each

processes of concrete production is observed in all observed sites of the projects.

5.6.2.3 Transporting and Placing of ConcreteOnce mixing of concrete ingredients is completed, it should be transported and placed at its

intended position or place as speedily as possible to avoid segregation, drying, etc. As it has been

discussed in the literature review, once concrete is discharged from the mixer, internal as well as

external forces start acting to separate the unlike constituents of concrete and if over-weight

concrete is confined in restricting forms, the coarser and heavier particles tend to settle and finer

and lighter materials tend to rise. This may cause segregation of particles which affects the

strength and overall quality of concrete.

Observation on project sites shows that concrete is transported vertically using winches by

pouring the mixed concrete in cylindrical barrels which can hold one mix at a time for

superstructure and using chutes usually made of corrugated iron sheets for substructure works.

Then shovels and flat open pan constructed with iron sheet usually known as "barella" is used to

transport and place in position. It is eminent that if concrete is to be transported for some

distance over rough ground the runs should be kept as short as possible since vibrations of this

nature can cause segregation of the materials in the mix. On the investigated sites it has been

observed that, concrete is not transported on rough surfaces while they use but it is poured into

cylindrical barrels then transported using winches and again discharged into a rough platform

then it will be transported and placed using shovels and "barrela" for superstructure works. Due

to this long and labor intensive processes, slump loss, segregation, loss of ingredients and

formation of cold joints may happen and also seen on some investigated sites.

It is eminent that, to avoid segregation and honeycombed concrete which usually have poor

strength and durability, concrete should not be dropped from a height of more than 1.5m.

Opposing this, in most of observed sites concrete is dropped from height of more than 2.8m

while they cast columns which are the major critical part of the building. The figure below shows

the most frequent placing method of columns in those projects.


Addis Ababa University, AAiTPage lxxx

Figure5.7.Common Concrete Placing of columns Practices in AAHDPO Projects

It can be observed from figure 5.7 that, rather than using buckets to place the concrete, shovels

were used as a means of placing of concrete from height which results segregation which brings

poor quality of concrete in terms of strength and durability. As a result a porous and segregated

columns and beams are observed in many concrete construction sites.

Discussion with respondents revealed that, lack of commitment in improving concrete quality is

observed with both contractors and consultants. Problem related to subcontracting of concrete

works by the contractors to laborers also leads in poor quality due to in need of to finish the

works within short period of time that brings difficulty in quality control of such works.

5.6.2.4 Compaction of ConcreteCompaction is the method of eliminating entrapped air from the concrete, either by means of

rodding, ramming or by vibrating. The purposes of compacting concrete being to obtain a dense

mass of concrete without voids, to get the concrete to surround all reinforcement and to fill all

corners. It has been discussed in literature review that during the process of manufacture of fresh

concrete a considerable amount of air is entrapped forming voids in it. Voids present in concrete


Addis Ababa University, AAiTPage lxxxi

in the form of small pores reduce the strength and density of concrete. Therefore proper

compaction shall be implemented to remove all those air from the concrete.

Compaction is done with vibrators in all visited sites and also respondents inform that it is

always under supervision to use vibrators. The problem observed on compaction is related to the

depth they use in compaction, vibrator center to center immersion and the angle they insert

vibrators. Proper use of immersion vibrators in terms of insertion time, center to center spacing

of vibrators poker immersion and depth of compaction are important for better result in concrete

compaction. However if there is negligence on these, bad concrete may be obtained from well

designed and produced mix.

Regarding to immersion vibrators used for concrete compaction in terms of insertion time, center

to center spacing of vibrators poker immersion and depth of compaction, nothing has been done

on site. Most of the investigated sites use common practices in compaction of concrete. Hence

attention shall be given by both contractors and consultants personnel for the compaction of

concrete in order to enhance the intended strength and durability of concrete.

5.6.2.5 Curing of ConcreteConcrete curing is the method of maintaining suitable moisture content and a favorable

temperature in concrete during the period immediately after the placement of concrete so that

hydration of cement may continue till the desired properties are developed sufficiently to meet

the requirements of service.

According to the interview with respondents, 85.1% of the respondents agreed curing is

maintained from 5 to 7 days for all concrete structures. The rest of 14.9% of respondents do not

agree and they revealed that the real practice of curing is not greater than three days.

According to observation on job sites, the degree of variability in sprinkling water varies from

contractor to contractor based on the level of supervision engaged from the consultants. In all the

investigated sites no burlaps or other covering materials is used to maintain the moisture of

concrete. Due to this reason the water sprayed over the concrete is not sufficient and efficient to

maintain the moisture in concrete throughout curing period. According to observation and

discussion with the respondents, shortage of water and lack of commitment by the contractors to


Addis Ababa University, AAiTPage lxxxii

do curing is observed. The way of transporting water is also a problem to higher floors because

they transport water using plastic jars for curing purpose. These may leads the laborers not to

supply enough water for concrete. Hence, consultants shall oblige the contractors to use pump by

to supply enough water for curing.

5.7 Concrete Quality Management of AAHDPOQuality management is concerned with preventing problems by creating the attitudes and

environment that make prevention possible. A critical quality management system in the project

context helps to turn stakeholder needs, wants, and expectations into requirements. In concrete

production, a quality of concrete which satisfies the required strength can be produced through

good implementation of quality management elements.

As it has been discussed on the literature review, project quality management includes all the

processes and activities of the performing organization that determine quality policies,

objectives, and responsibilities so that the project will satisfy the needs for which it was

undertaken. It implements the quality management system through the policy, procedures, and

processes of quality planning, quality assurance, and quality control, with continuous process

improvement activities conducted throughout, as appropriate.

Though the implementation of quality management system (QMS) helps in improving the quality

of concrete and other significant feature of works, stakeholders who are responsible for these

projects implement the quality management system in poor level.

Based on an interview with experts, Table 5.5 below summarizes the implementation quality

management system of Addis Ababa Housing projects.

Table 5.5 Implementation of QMS in AAHDPO Projects

Implementation of QMS

in AAHDPO Projects

Yes, there is 7.80%

To some extent 70.92%


Addis Ababa University, AAiTPage lxxxiii

Not, at all 21.28%

As it is shown in Table 5.5 above, 7.8% of respondents agreed with the implementation of the

quality management system whereas 70.92% of respondents agreed that the implementation is to

some extent and the remaining 21.28% disagree with other respondents and they say that there is

no quality management system at all. From desk study and observation, the quality management

system is there in some written form of the contract documents but the problem relates to the

proper organization of those documents and implementation of procedures with a committed

stakeholders.

Regarding to the advantages of quality management plan (QMP), 95.74% of experts agreed on

the advantage obtained from QMP and the rest 4.26% of respondents do not accept the advantage

and their reason is related to much of work paper. However, discussion with experts reveals that

there is no quality management plan document which offers vital information and guide about

any significant works related to quality assurance (QA) and quality control (QC) in practice.

Usually checklists and compressive strength test results conducted on concrete are considered as

the only control measure on those public projects.

Even having a written and well organized quality management system do not guarantee the

improvement of quality of the product. Hence, management commitment and qualification of

personnel who participate in the production of concrete is very fundamental. Bearing in mind

this, in succeeding topics the author discusses the views of respondent.

5.7.1 Management CommitmentThe role of quality management for a project is not an isolated activity, but intertwined with all

the operational and managerial processes of the project. As it has been discussed in the

introduction part of this chapter, this project is a government led project with the aim of

achieving low cost but quality houses to all house seekers in the city and many consultants,

contractors and SME's are participated in the construction to achieve the intended goal of the

client. Therefore, the quality of concrete and the overall project quality are accomplished through

an integrated effort and commitment between all levels of managers and their organization to


Addis Ababa University, AAiTPage lxxxiv

realize the intended quality by continuously improving current performance of concrete

production practice.

Regarding to management commitment to improve the current level of concrete production, the

experts are interviewed and they respond as it is summarized in Table 5.6 below.

Table 5.6 Management Commitment to improve concrete production in AAHDPO projects

Organization

Management and Personnel Commitment

Satisfactory Fair Satisfactory Less Satisfactory

Client/AAHDPO 10.64% 65.96% 23.40%

Consultants 14.89% 59.57% 25.53%

Contractors 0.00% 44.68% 55.32%

As it is shown in the table 5.6 above, the efforts of those three main stakeholders in concrete

quality improvement varies based on the views of respondents. According to the result, only

10.64% of respondents agreed that the effort made by the client is satisfactory and 65.96% of

them say fair satisfactory and the remaining 23.4% believed as less satisfactory. When we see

the efforts of consultants based on the interview, only 14.89% of the respondents stated as it is

satisfactory while 59.57% of respondents state fair satisfactory and the remaining 25.53%

believed as it is less satisfactory. Regarding to the contractor, none (0.0%) of the respondents

satisfied with while 44.68% says fair satisfactory and the remaining 55.32% thought as it is less

satisfactory.

Following the respondents comment, desk study and observation, all stakeholders have

commitment problems and lack of professional ethics in the improvement of quality on those

projects. Some of the respondents also posited that, there is a perception of considering

condominium buildings as low quality buildings. Hence, by avoiding misleading perceptions and

by applying proper management commitment within all organizations who participate in these

public projects it can be possible to enhance the level of quality of site concrete production.

5.7.2 Companies and Personnel QualificationQualified and knowledgeable personnel in any concrete construction are essential for producing

quality concrete. The contract document used in AAHDPO for both consultants and contractors


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define job qualification requirements, including necessary educational qualifications, experience

and scope of responsibilities for personnel in supervision and construction of works.

Respondent's opinion regarding to the adequacy of consulting and constructing companies in the

production of concrete and its improvement based on their experience and manpower availability

was collected and summarized in table 5.7 below.

Table 5.7 Adequacy of companies and personnel to enhance concrete quality of AAHDPO

projects

AdequacyYes No

Consulting Companies 74.47% 25.53%

Construction Companies/Contractors 34.04% 65.96%Qualified personnel including skilled andnon-skilled labors 59.57% 40.43%

Based on consultant's capability, availability of professionals and their experience, 74.47% of the

respondents stated that the consulting companies are adequate to enhance the quality of concrete

whereas 25.53% of respondents disagree with the adequacy of the consultants.

To increase the quality of concrete, professionals who trained in higher educational institutions

and have good work experience shall be participated in all concrete construction processes

including the supervision and quality control. Apart from this, most of consultants hire graduate

engineers who have zero year working experience as a site inspector and all the quality is

controlled and approved by those fresh engineers to get cheap manpower. This problem

contradicts with the contract document which specifies at least 2 years of experience and higher

level education to site inspectors. According to observation and contract document, each

engineer inspect at least six blocks which is difficult to control every work procedures. Hence,

proper control of the consultants by the client is obliging to get a qualified professional in

sufficient amount which may help in the improvement of concrete quality.

Referring to contractor's capability, resource availability and their experience in similar projects,

only 34.04% of experts agreed on their adequacy in the improvement of the quality concrete

where as 65.96% strongly disagree on the adequacy of contractors and their professionals. If

these concrete producers are not adequate in producing concrete it is difficult to obtain a quality


Addis Ababa University, AAiTPage lxxxvi

building product. Therefore, strong measures shall be taken by the client to improve the level of

contractors. One crucial method is a capacity building program using training and certification of

professionals who participate on those projects. This is done by AAHDPO but it is not in

sufficient amount because if continuous improvement is needed a continuous training and

support for those contractors are mandatory.

According to the contract document of this project, contractors shall have an engineer with least

a BSc degree or advanced diploma in civil engineering or related fields and have at least 4 and 6

years of experience respectively. It also states a general foreman with diploma and at least 4

years of experience. This is good to specify a minimum qualification for professionals in the

improvement of quality of those projects. From observation and interview on job site, most of

the contractors have only Foreman’s who manage and control the concrete production and other

works on site. This has been seen as a major issue in concrete production by contractors which

bring poor control of the production process with only one person. Hence, consultants and the

client shall have a check and balance system in the availability of sufficient professionals to

maintain the project quality.

5.7.3. Manpower and WorkmanshipIn the production of quality concrete extreme care must be exercised at every stage so as to

obtain the desired results. All suitable precautions must be taken to ensure proper inspection of

the ingredients, batching, mixing, transporting and placing. Quality control of concrete demands

a high degree of carefulness among all personnel connected with the production.

In site concrete production, there is a high demand of manpower who participates in all processes

of concrete production to have a good workmanship. Therefore, the construction industry shall

respond for manpower by providing manpower of a quality and capacity to undertake this work

successfully.

Observation reveals that, the actual concrete production trend in these projects is far from this

and it is difficult to get qualified and trained skilled and semi-skilled laborers who do their work

skillfully. According to respondents from those projects 59.57% agreed the availability and

adequacy of skilled and semi-skilled laborers and the remaining 41.43% don't agree with the

availability and adequacy of workmanship on these projects. Some respondents posited that, lack


Addis Ababa University, AAiTPage lxxxvii

of this skilled manpower is related to the wages paid to them and challenges related to farness of

the project which is usually at the outskirts of Addis Ababa. This is greatly affecting the

workmanship of the project products from intended quality.

CHAPTER SIX

CONCLUSIONS AND RECOMMENDATIONSFrom the study made on Addis Ababa housing projects regarding to the quality of site concrete

production and the management practice, it have been seen that a number of problems related to

concrete production and quality management practices exist on those projects. Therefore, this

chapter presents the conclusion it reaches and the recommendations drawn out from the

assessment carry out on those public building projects.


Addis Ababa University, AAiTPage lxxxviii

6.1 Conclusions1. Statistical quality control analysis based on compressive strength test results reveals that, the

quality of concrete produced on those public projects have higher uncertainties and varies

from good to bad. From the compressive strength of test result, 40.4% of test results found to

be defective according to compliance criteria’s of EBCS-2:1995 where as 31.25% of the test

results found to be defective according to ACI-318 compliance criteria’s.

2. The level of quality control of concrete production has also a greater uncertainty and is not

good enough. Based on ACI-214 classification and considering their standard deviations and

coefficient of variations, a significant amount is fall under “fair” and “poor” categories.

According to this classification, 35.4% of test result’s standard deviations show the level of

quality control practiced is not good and among this 8.75% are fall under “fair” range and the

remaining 26.65% falls under “poor” range. Based on their coefficient of variation 71.25% of

compressive test results shows the quality control is not good and among these 8.75% fall

under “fair” range and the remaining 62.5% falls under “poor” range.

3. Even if these projects uses potable water for concrete production, most of the water tankers

are open which are contaminated by dusts and other impurities from the surroundings which

fundamentally affect the overall concrete quality.

4. Two most frequent mistakes are commonly practiced in concrete batching which related to

poor precision in batching. They are commonly called under batching and over batching

which leads to variations in the properties and the quality of the produced concrete. In

addition to this, the use of sands and aggregates without adjustment of bulking sand effect

and absorption capacity is commonly practiced.

5. Concrete for columns are placed using shovels from the height of more than 2.8m in most

projects. Therefore, bad placing method of concrete is practiced that might cause the

segregation of concrete ingredients and brings poor quality concrete product.

6. From observation and discussion with experts, the curing practice in AAHDPO projects

varies from good to poor. No covering sheets are used at all to retain the moisture and water

is sprayed using plastic jar in deficient amount.

7. Preparing and implementing quality management system (QMS) in concrete production

greatly helps in improving the quality of concrete. On contrary, 7.8% of interviewed

respondents agreed with the implementation of the quality management system on those


Addis Ababa University, AAiTPage lxxxix

projects whereas 70.92% of respondents agreed that the implementation is to some extent and

the remaining 21.28% respondents believe that ,there is no quality management system at

all.

8. From observation and interview, there is lack of management commitment problems by the

three stakeholders i.e., client, consultants and contractors in the improvement of concrete

quality. In addition to this, lack of professional ethics and perception in understanding those

public projects as low quality houses rather than aware as low cost houses are the major

causes of quality problems of concrete production on those projects.

9. Be deficient in experienced construction companies and trained personnel which help in

providing a quality concrete product is one cause which hinders quality concrete production.

On the other hand, lack of supervision consultant’s personnel experiences, which supervise

and control the project, are also a problem in concrete production. In addition, problem to get

qualified and trained skilled and semi-skilled labourers who do their work skilfully is the

cause that related to poor workmanship which brings poor quality of concrete.

6.2 Recommendations1. Clients and consultants must first implement a thorough investigation and testing of

concrete materials i.e., water for the concrete, aggregates and cement within the project

location and carry out initial laboratory investigations of the presence of deleterious

substances on them and other necessary testing parameters before issuing approval for their

consumption for concrete production works. Thereafter both the consultants and the

contractors must collaborate to carry out detailed confirmatory laboratory tests of fitness of

all such materials before bulk procurement and continuously when these retesting is needed.

In addition, standard care should be given while handling and stockpiling of those concrete

materials.

2. Attentive care shall be taken to all concrete production process by implementing a well-

organized quality management system that can be achieved with well trained and

experienced professionals who understands the rewards and consequences of each process

that contribute to the quality of the final product.


Addis Ababa University, AAiTPage xc

3. Manual concrete production is labour intensive and needs very careful quality control at

every stage of the concrete production process which is difficult to achieve such mega

projects which fits to its purpose. Therefore, the use of central automated batching plants for

those projects greatly helps in the production of a quality concrete product that can be

controlled at the central unit. This on the other hand may help in reducing the cement

consumption by reducing errors from batching and other variations caused due to the

production processes of concrete.

4. There must be utilization of qualified and experienced personnel for all stakeholders

participating in AAHDPO projects right at the top management level to the site manager,

construction coordinators, supervisors, skilled and semi-skilled labourers and even to

unskilled labourers and other categories of workers which participate in concrete production

line.

5. There shall be quality policies, regulations and manual assisting the development of a

quality management plan document for concrete production, which must be adhered,

through a committed management system of all direct stakeholders

6. Providing a continuous capacity building program for those stakeholders who participate in

Addis Ababa housing projects by AAHDPO is crucial to enhance the capacity of the

consultants, contractors and their personnel.

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APPENDICES


Addis Ababa University, AAiTPage xcv

APPENDIX-I


Addis Ababa University, AAiTPage xcvi

Addis Ababa Institute of Technology (AAiT)

School of Civil and Environmental Engineering

MSC Program in Construction Technology and Management

Research Title: Study on Quality of Site Concrete Production and itsManagement Practice in Addis Ababa Housing Projects:

Case Study on Koye Feche Housing Project Program

Research By: Habtamu Sisay


Addis Ababa University, AAiTPage xcvii

Dear Sir/madam

Thank you for taking your precious time to respond for this interview questions. This interview

questions are a research instrument for fulfillment of my MSc thesis. My research topic title is

“Study on quality of site concrete production and its management practice in Addis Ababa

housing development projects: A case of Kuye Feche housing project program”.

The questionnaires listed below are attempted to respond the current concrete production and

management practices employed in Addis Ababa Housing projects. Hence, your responses are

highly valuable to finalize my research.

I kindly need to confirm that, your responses are completely anonymous and confidential, and

will not be identified by individual. Your responses are used exclusively for only this research

and all responses are compiled together and analyzed as a group.

Thank you very much for taking your time to answer the interview questionnaire.

With regards,

Habtamu Sisay


Addis Ababa University, AAiTPage xcviii

1.3 Objective of the study

The purposes of this research are to:

Investigate the quality of site concrete production in Addis Ababa Housing projects.

Investigate concrete quality management practices on those projects

Examine the quality of concrete produced by considering their compressive strength via

taking sample specimens from ongoing projects from selected sample sites at Koye Feche

housing project.


Addis Ababa University, AAiTPage xcix

1. Please specify your field of study.

2. Please specify your highest level of education

High school diploma TVET Certificate Diploma BSc MSc

3. Please specify your years of experience:

< 2 years 2-4years 4-6 years >6years

4. Your current position in your company

Resident engineer Site engineer Office engineer Quality Manager

Please write any other position, if any: ____________________________________

5. What is the type of organization you are working?

Client Consultant Contractor

6. Please specify your company license category, grade and years of experience in building

construction projects.

7. How do you control quality of concrete produced at site? Regarding materials, concrete

production process and workmanship.

8. What parameters and test you check and conduct on concrete materials? Please specify if

any

a. Tests conducted on cement (soundness, age & etc.)

b. Tests conducted on coarse aggregates? How often you take sample for test


Addis Ababa University, AAiTPage c

c. Tests conducted on fine aggregates/sand. How often you take sample? Do you

have any reliable source?

d. Tests conducted on reinforcement bar. How often you take sample?

e. Tests conducted on water if any. Is the water potable (drinkable) or you are using

other sources for concrete production? Please specify if any,

9. What precaution measures you take in batching concrete? Related to box sizes,

adjustments of bulking effect of sand, absorption capacity of aggregate and etc.

10. What precaution measures you take in concrete mixing? Regarding to mixer volume, type

and status, mixing time, workmanship and etc.

11. What precaution and corrective measures you take in concrete transporting and placing?

Horizontally and vertically in related to segregation, slump loss, loss of ingredients and

formation of cold joints.

12. What precaution measures you take in concrete compaction to avoid honeycombed

concrete or to remove the entrapped air.


Addis Ababa University, AAiTPage ci

13. What precaution and corrective measure you take in concrete curing? In related to the

application of water spraying or covering sheets, period for curing of casted concrete

while you use different type of cement like OPC or PPC.

14. In your opinion, do you think the quality of concrete used in Koye Feche sites are better-

quality? Please specify your reasons.

15. In your opinion, do you think the efforts and commitments of direct stakeholders on those

projects to improve quality of concrete are satisfactory? Please specify your reasons.

Regarding to

a. Client(AAHDPO office)

b. Consultants

c. Contractors

16. Is there any Total Quality Management (TQM) system in place to ensure quality of site

concrete production on those projects?

17. Do you think concrete quality management plan is essential to improve quality of

concrete produced at site?

18. Does your company have any quality management plan document for concrete and other

definable work items in building construction?


Addis Ababa University, AAiTPage cii

19. Does your company have quality control/quality assurance policy, team or department?

20. Do you think adequate companies, professionals and skilled workmanship are available

to enhance the quality of concrete produced on those public projects? Regarding to

a. Consulting Companies

b. Construction companies/ Contractors

c. Professionals participating on those projects

d. Skilled and semi skilled laborers

21. What preventive and control methods you advice in order to enhance the current

concrete production practices on those public projects?

22. Please list any comment and suggestion you have.

Thank you for your cooperation!


Addis Ababa University, AAiTPage ciii


Addis Ababa University, AAiTPage civ

APPENDIX-II


Addis Ababa University, AAiTPage cv

Addis Ababa Institute of Technology

Department of Civil and Environmental Engineering

Proposed Quality Management Plan for Concreting

Works in AAHDPO Projects

Version One

March, 2017







Version One

March, 2017







Version One

March, 2017


Addis Ababa University, AAiTPage cvi

Table of Contents

Section1.Introduction…………………............................................……………………………………..……....1

1.1 Project Setting……………….......................................….........……………………..….............2

1.2 Quality Program Overview……………………..............………………….……….….…........2

1.3 Quality Control………………………………….........................………….…….……...….......4

1.3.1 Quality Control PlanPhases………………………...................……........................................................………...5

1.3.2 Plans and Specifications………………………………………….........……....….6

1.3.3 Pre- ConstructionsConference………………………......................….….…..........................................…..…...7

1.3.4 Equipment Proposal…………………………………………...........................…..7

1.3.5 Labor Enforcement………………………………………………..........................7

1.3.6 Storage of Materials……………………………………….............……................8

1.4 Quality Management Plan……………………………………………………...........................9

1.5 Organization of AAHDPO Projects Quality Control Plan………………...................….....9

Section 2. Project Quality Control Organization………………...............................….....…11

2.1 Responsibilities and Authorities of Organizations…………………..........................….......11

2.1.1 AAHDPO……………………………......................................................…......…..10

2.1.2 Consultants……………………………………..........................................................11

2.1.3 Constructions Constructor……………………………………….........................12

2.2 Structure of Quality Control Organization…………………………………….…….....…...12

2.3 Responsibilities and Authorities of Key Personnel…………………..........................….....13

2.3.1 Consultant’s Quality Control Personnel………………........................................13

2.3.2 Contractor’s Quality Control Personnel……………....………...........................…....17

Section 3. Submittals.............................................................................................................17

3.1 Submittal Schedule………………………………………………………………................…17

3.2 Process, Review and Acceptance…………………………………………….....….…..........18

3.3 Storage……………………………………………………………………………….................20

Section 4. Performance Monitoring Requirements…………………………......….......…...21

4.1 Environmental Protection Plan……………………………………………….................21

4.1.1 Contractor’s Responsibilities……………………………….............……...........21


Addis Ababa University, AAiTPage cvii

4.1.2 Key Activities for Monitoring During Construction………………......…........21

4.2 Reporting……………………………………………………………………........…....21

4.2.1 Quality Control Report………………….............……......…………................23

4.2.2 Progress Schedules……………………………………………....................….24

Section 5. Inspection and Verification Activities…………….……………...….........…...25

5.1 General Construction Inspection & Verification Requirements……….............25

5.1.1 Inspections……………………………………………………......................…26

5.1.2 Contractor Concrete Quality Control Testing……………………...........…......28

5.1.3 Consultant’s Quality Control Testing……………………………….................29

5.2 Construction Acceptance Criteria………………………………..................….31

5.3 Compliance with Handling, Storage, Packaging, Preservation

and Delivery Requirements…………................................................................................31

5.4 Material Identification and Traceability…………………………………….................31

Section 6. Construction Deficiencies………………......................................................…33

6.1 Deficiency Identification………………………………………………………...........33

6.2 Quality Control Deficiency Identification and Control…………………….......……..33

6.3 Quality Control Deficiency Correction………………………………………..............34

6.4 Preventive Actions………………………………………………………….................35

Section7. Documentation……………………...........................................……........……...37

7.1 Daily Record Keeping…………………………………………………….......……....37

7.2 Daily Construction Report…………………………………………………….........…37

7.3 Inspection and Testing Report Forms………………………………………........…....38

7.4 Control of Quality Records…………………………………………………...........…39

Section 8. Field Revisions………………………………………………..…………........…...40

8.1 Quality Control Plan Revisions…………………………………………….................40

8.2 Contractors Quality Plan Revisions………………………………………...............…40

Section 9. Final Reporting…………………….....................…………………...............….42

9.1 Work Completion Report:…………………………………………….........………....42

Section10. References…………………………………………………………………….......42

Section 11. Appendices…………………………………………………………………….…43


Addis Ababa University, AAiTPage cviii

AppendixA:Sample Qualification Test Schedules…………………….....................…......44

Table A-1: Qualification Test Schedulefor concrete making materials……...........45

Table A-2: Qualification Test Schedule for cementations…………......................46

Table A-3: Qualification Test Schedule for Concerete mix field tests…….….......46

Appendix B:Sample Inspection Schedules…………………………………………......…47

Table B-1:Inspection Schedule for aggregate placement…………........……... ….48

Table B-2 : Inspection Schedule for reinforcing,formwork and cast

In-situ concrete.......................................................................................................49

Appendix C:Sample test Schedules…………………………….......... ……………. ....…50

Table C-1: Testing Schedule for Concrete………………………..............….......…51

Appendix D: Typical Construction forms……………………………………….…..….….53

List of Figures

Figure1.1 Balanced Triangle Constraints for Projects…………………………….......…..…2

Figure 2-1 Quality Control Organization for Addis Ababa Housing Projects………...……13


Addis Ababa University, AAiTPage cix

Glossary of Acronyms

AAHDPO Addis Ababa Housing Development project office

ACI American Concrete Institute

ASTM American Society for Testing and Materials

CQA Concrete Quality Assurance

CQAP Concrete Quality Assurance Plan

CQCP Concrete Quality Control Plan

CQCM Consultant’s Quality Control Manager

CQMP Concrete Quality Management plan

EPP Environmental Protection Plan

EBCS Ethiopian Building Code of Standards

NCR Non-Conformance Report

PM Project Manager

RE Resident Engineer

QA Quality Assurance

QC Quality Control

QCM Quality Control Systems Manager

QCP Quality Control Plan

QMP Quality Management Plan

QMS Quality Management System

SECTION 1

INTRODUCTION

Project Quality Management Plan (QMP) is an essential document that any contractor or

consultant must have. It is the life line of a project that will ensure the end product that is going

to be delivered to client meet all the requirement and specifications. This project quality

management plan for concreting activities (CQMP) document offers vital information about

concrete materials related to quality assurance (QA) and quality control (QC) practices for Addis

Ababa housing development project office (AAHDPO) condominium building projects with

much significant concrete structures. It is the researcher’s intention that this document serves as

a guide for developing a QMP for concrete construction of significant concrete structures of

AAHDPO projects. The project management team, consultants and contractors should prepare

and use QMP documents (project-specific QC and QA procedures) which are appropriate and

fits to a given project. This document grants information about what to include and items to

consider for QC and QA planning.

Quality is enhanced by working systematically, according to formalized procedures, designed to

prevent or eliminate errors from occurring. It is the adherence and conformance to properly

developed requirements. Requirements for quality design in concrete construction include

conformance with applicable codes, standards, guidance, regulations, laws, and statues

referenced in the specifications. Requirements for quality construction also include compliance

with contract provisions, clauses, and specifications. These contract documents establish the

quality requirements for construction by defining the standards, including salient and essential

characteristics, of concrete materials and the acceptance criteria and necessary testing inspection

of concrete construction.

It shall be the responsibility of AAHDPO Project Managers and Consultants to ensure that this

concrete quality management plan (CQMP) procedures are implemented consistently and

effectively and that they are reviewed regularly to reflect the requirements of the contracts

throughout the durations of works. It shall be the responsibility of the quality control manager to

constantly monitor the implementation of quality control plan to establish and put into practice

necessary systems and procedure, and ensure adherence to the quality control plan through

regular auditing.


Addis Ababa University, AAiTPage 2

1.1 Project Setting

Addis Ababa Housing project office (AAHDPO) is the main administrator organization for the

overall construction and management of housing projects in Addis Ababa under Addis Ababa

City administration. The project is funded by Addis Ababa City administration and with a loan

from commercial bank of Ethiopia (CBE). The projects are typical condominium buildings

which are located on different selected location of Addis Ababa city. AAHDPO is responsible

and administrator of those projects from inception to completion of every single project. The

office is accountable for overall project management and quality construction of the buildings.

Figure1.1 Balanced Triangle Constraints for Projects

The diagram above represents the balanced triangle constraints for the projects. Any change to

one of the constraints will affect the other constraints, which will require a re-balancing of all the

constraints. Therefore, it is the intention of this document to propose and develop a suitable

concrete quality management plan (CQMP) for housing projects, which is crucial to ensure the

achievement of right quality concrete structures at a right cost and at a right time.

1.2 Quality Program Overview

Under the terms of the work agreement with AAHDPO, assigned consultants for each project are

responsible for quality control and quality assurance of the overall construction including

concrete structures which are the main and critical members of the buildings.



The quality control plan details the systems and controls those consultants have to put in place so

that the quality of the concrete structure and overall construction will meet the requirement

specified by the contract agreement. The quality of Addis Ababa housing projects will be

ensured through an integrated system of quality control and quality assurance performed by

assigned stakeholders and they are responsible for the day-to-day coordination of quality

measures in the field.

Should there be any contradiction between the contract agreement and the quality control plan,

the contract agreement shall prevail. The quality control plan establishes,

Project procedures and general responsibilities for the quality control program, and

Protocols to ensure that the construction plan will be executed in accordance with the

related requirements

Hired consultants will be responsible for the follow up of the construction work to be carryout in

accordance with the plans and specifications. Consultant’s quality control plan is the systematic

implementation of a program of inspections and production control to attain the required

standards of quality and to prevent problems resulting from noncompliance.

Corresponding to contract’s technical specification, each construction contractor will establish an

independent QC program in line with the consultants CQCP and write a contractor concrete

quality control plan (CCQCP). The contractor quality control plan shall provide for test and

inspections pursuant to various technical specifications. It will define procedures to ensure that

activities affecting quality are properly documented and accomplished in accordance with

contract documents such as written instructions, codes and procedures. Furthermore, the

contractor quality control plan will define methods for ensuring that activities affecting quality

will be accomplished under controlled conditions.

Independently of the construction contractors, consultants’ engineer will provide quality control

through daily monitoring and scheduled inspections to verify the effectiveness of the contractor’s

quality control program and assure that the quality and contract requirements are met the

contractors. The Engineer assures that the contractor’s quality control is working effectively and



the resulting construction complies with the quality requirements establish by contract and codes

of standards established for good concrete production.

The objectives of this Concrete Quality Control Plan are to:

Describe a quality program to be implemented so that the project concrete structures are

constructed in accordance with the contract requirements,

Describe guidelines for inspection and documentation of concrete constructions activities,

Provide reasonable assurance that the completed work will meet or exceed the

requirements of the constructions drawings and specifications, and

Describe how any unexpected changes or conditions that could affect concrete

construction quality will be detected, documented and addressed during construction.

1.3 Quality Control

The role of consultant’s quality control manager is to assure that the quality requirements of

Addis Ababa housing projects office have been satisfied.

The quality control plan requires that the construction contractors implement the program and

use its provisions daily to control quality of the work. Effective quality control requires a serious

and concentrated effort on the part of the supervisory and inspection personnel. The tools for the

accomplishment of effective quality control are as follow:

Quality control personnel are expected to have the necessary education, experience and

capability.

Before start of construction, the consultants quality control manager shall conduct a

mutual understanding meeting with the contractor and discuss the contractor’s quality

control system, construction start will be delayed until after the mutual understanding

meeting and submittal/ acceptance of at least the interim contractor concrete quality

control plan. The contractor quality control plan will be critically examined.

The consultant’s quality control manager will assure that the contractor concrete quality

control plan is sufficient to obtain quality of concrete construction designed in the

contract plans and specifications.



1.3.1 Quality Control Plan Phases

This quality control plan will comprise the following three phases:

Preparatory phase meetings: Quality control meetings will be held before each

definable feature of work is executed to ensure that the documentation is complete,

materials are on hand, and the construction workers, who are to perform the work,

understand what they need to know about the feature of work. Both the actual contract

specifications and those referenced in the contract specifications shall be in the

contractor’s library and available to the quality control inspections, as if the quality

control inspectors do not have the required specifications, they cannot know or enforce

the provisions of the specifications.

Initial Inspections: Quality control inspections shall be conducted in a timely manner at

the beginning of a concrete construction work. A check of the preliminary work will

determine whether or not the contractor, through his contractor quality control system

and the workmen involved, thoroughly understand and is capable of accomplishing the

work as specified.

Follow-up Inspections: Also conducted by consultant’s quality control staff and

contractor’s quality control staff, such inspections will be done daily when concrete work

is in progress and are for the purpose of assuring that the controls established in the

earlier phases of inspection continue to provide work which conforms to the contract

requirements. Most of the comments in both the contractor quality control and quality

assurance daily reports will be generated from these inspections.

In all projects, there is work that is ‘cut and cover’ that is, work that cannot be inspected “after

the fact”. Good example for this is concrete where the size, number and location of reinforcing

steel, amount of concrete materials used and production which cannot be readily determined after

the concrete is placed. Hence work of this nature shall be closely controlled and monitored to

avoid poor quality of product.

The consultant’s CQCP has a vital role in assuring good quality and avoids poor quality from

occurring. Responsibility for compliance shall not be left wholly to the contractor.



The consultant’s quality control manager shall closely monitor the contractor quality control

program to assure that the three-phase control system is being correctly performed and that the

contractor is effectively controlling all operations. In the event that contractor quality control

personnel are not capable and are not inspecting properly, the resident engineer shall be notified

immediately and shall correct performance by using one or more of the enforcement tools

provided for in the constructions contract. Records and reports will document all such facts.

1.3.2 Plans and Specifications

Consultant’s quality control manager will monitor the preparation of design documentation

including plans and specifications, and will:

Watch for omissions,

Watch for discrepancies between plans and specifications,

Check plans and specifications against requirements of which problems occurred on

similar jobs,

Compare elevations, grades and details shown on plans as exiting, with those at the actual

site,

Report all errors, omissions, discrepancies, and deficiencies to the design office and

resident engineer, and

Always keep a posted and marked up set of plans and specifications convenient for ready

reference.

As a consultant, quality control managers shall anticipate the construction contractor’s operations

by reviewing the plans and specifications for each operation before it begins, and:

Discuss contract requirements in each preparatory phase meeting with the constructions

contractor before each operation begins, and

Highlight and/or make notes of those provisions which need special attention, such as:

Unusual requirements

Those which other contractors have overlooked

Repetitive deficiencies



Use the checklists in these guides to help find significant items in the plans and

specifications.

1.3.3 Pre-Constructions Conference

The quality control officer, resident engineer and contractor representative shall attend pre-

construction conference, in addition to AAHDPO project manager and its designated quality

assurance representatives. Minutes of the conference shall be available to each of the quality

assurance/quality control representatives assigned. The subject of the proposed quality control

plan shall be well documented.

1.3.4 Equipment Proposal

All equipment proposed by the contractors in site concrete production processes used in mixing,

conveying, placing and compacting the concrete shall be approved by the consultants prior to its

use.

All the necessary equipment for any particular pour shall be on site and proven to be in working

condition before the pour commences, with backup equipment on site as determined by the

consultant.

The equipment shall be well maintained, suitable in kind and adequate in capacity for the

concrete work.

Consultant’s checklist for equipments used in concrete production shall:

Check appropriateness of the capacity and the speed of rotation of the mixing drum or

blades of the mixers used for concrete production from manufacturers specification

proposed by contractors,

Ensure that all joints, valves and other parts of the mixer shall be maintained so that there is

no leakage of water or cement paste out of the mixer drum,

Ensure that concrete transportation equipments used shall minimize segregation that caused

due to transportation and placing,

Ensure vibrators shall be of a type and design adequate for intended use,

Ensure sufficient number of vibrators is available to properly compact each batch

immediately after the concrete has been placed in the forms.



1.3.5 Labor Enforcement

Consultants and supervisors checklist for labor enforcement shall:

Check sufficient laborers are there for the production of concrete,

Ensure that skilled workers understand ways of improving concrete quality,

Promptly inform the resident engineer and contractors authorized personnel of any labor

problems and disputes that may disturb the concrete working environment,

Assist all personnel in assuring quality,

Ensure that each laborer and equipment shall be classified in accordance with the

particular work function.

1.3.6 Storage of Materials

Consultant’s checklist for storage of materials:

Ensure that adequate space is available for the contractor’s operations and storage areas,

Ensure all storage areas are adequate for storing concrete making materials,

Ensure that approval has been obtained for temporary sheds, buildings, etc. which the

contractor proposes to install at the site for cement and other concreting materials,

Ensure that concrete materials and equipments are properly stored and protected,

Ensure that safety requirements necessary for specific project,

Ensure that all concrete making materials are available to produce desired concrete

amount.

1.4 Quality Management Plan

Contractors will carry out the construction work of Addis Ababa Housing projects in accordance

with this concrete quality management plan (CQMP) which will helps in managing and

improving quality of concrete and other works.



1.5 Organization of Concrete Quality Management Plan forAAHDPO projects

This Concrete Quality Control Plan is organized into eleven sections.

Section 1- Introduction: Describes the project setting, the contract and related documents,

and the Quality Control plan overview.

Section 2- Project quality control Organization: Presents the organization and key

personnel involved in the construction of Addis Ababa Housing projects, their

responsibilities and authorities, the structure of the quality control organization and the

minimum suggested training and experience of the quality control officer and personnel.

Section 3-Submittals: presents the procedures for processing submittal from contractors

and vendors.

Section 4- Performance Monitoring Requirements: Addresses quality control for

performance monitoring requirements.

Section 5- Inspection and verification Activities: Provides procedures for tracking

construction inspection and verification activities for the contract, and construction

acceptance criteria and construction audits.

Section 6- Construction Deficiencies: Describes the procedures for tracking construction

deficiencies from identification through acceptable corrective action.

Section 7- Documentation: Describes the procedures for the project documents that will

be managed through a combination of a secure documents filing and storage system and

computerize document tracking system.

Section 8- Field Changes: Describes handling of quality plan changes to assure quality

control objective are met.

Section 9- Final Reporting: Describes the quality control documentation

Section 10- References: Provides bibliographic references to key document referred to in

the body of the plan.

Section11- Appendixes: Provides different concrete quality control and quality assurance

formats.



SECTION 2

PROJECT QUALITY CONTROL/QUALITY ASSURANCEORGANIZATION

This section presents the responsibilities and authorities of organizations and key personnel

involved in the construction of Addis Ababa housing projects, the structure of the quality control

organization, the minimum training and experience of the quality control personnel and the

quality control training given to all onsite works including concrete work.

2.1 Responsibilities and Authorities of Organizations

The organizations involved in the Addis Ababa Housing projects and their quality control roles

and responsibilities are as follows.

2.1.1 Addis Ababa Housing Development Project Office

The AAHDPO is the lead agency responsible for observing and monitoring the progress of the

projects and all administration works. It allocates portions of each project to individual

contractors. It also allocates and supplies concrete construction materials such as reinforcement

bar, cement, aggregate and finishing materials including electrical and sanitary fixtures.

AAHDPO also assigns AAHDPO sub-branches on project site location and consultants for each

project which controls and manages the allocated projects.

Each sub-branch project offices are responsible for overall project management of buildings

under each project. They are also responsible and control whether consultants and contractors are

working in accordance with the contract documents or not. They are organized to follow the

progress of the work and overall management and take corrective measures when problems arise.

2.1.2 Consultants

The consultant is responsible for maintaining quality control ensuring that contractors and

subcontractors



perform the construction works in accordance with the contract documents, specifications, and

related documents. The quality control plan details the systems client and consultant have put in

place in order ensure that quality requirements are met.

The consultant’s resident engineer/representative provides professional construction project

management and related services in connection with the project. The Resident

Engineer/representative is responsible for implementation of this concrete quality control plan

(CQMP). The resident engineer will manage construction contractors on behalf of the consultant

and serve as the primary point of contact with the contractors for all communications to and from

the contractors. The resident engineer will provide quality control and monitor the day-by-day

construction quality control activities performed by construction contractors to verify compliance

with the contract plans and specifications. The resident engineer will also manage, coordinate,

and administer all quality control activities and requirements, including subcontractors involving

in AAHDPO projects.

2.1.3 Construction Constructors/Contractors.

The construction contractors are hired by Addis Ababa housing development project office to

provide the labor work. In case of concrete construction on those projects sand and equipments

such as mixer and vibrators are provided by the contractor in accordance with the contract

documents.

Construction contractors are responsible for the quality control of their constructed work product

as well as the necessary inspections and tests required to ensure that their work complies with the

contract documents. They exercise authority over their workforce, including quality control

personnel and their third-party quality control support services, if any. Each contractor will have

to submit a quality control organization chart developed to show all quality control personnel and

how these personnel integrate with other management, production and construction functions and

personnel to the consultant. All quality control staff members are subject to acceptance by the

consultant. The requirement for the quality control organization includes a quality control

systems manager and a sufficient number of additional qualified personnel to ensure contract

compliance. The contractor is expected to provide a quality control organization that is



represented on the site at all times during progress of the work and with authority to take any

action necessary to ensure compliance with the contract.

2.2 Structure of Quality Control Organization

The quality control and quality assurance functions of the project organizations will be

functionally integrated although contractually separate. Figure 2.1 shows the functional structure

of the project quality control team.

Figure 2-1 Quality Control Organization for Addis Ababa Housing Projects



2.3 Responsibilities and Authorities of Key Personnel

Quality control representatives shall be thoroughly familiar with all the provisions of the contract

documents, including submittals. Plans and specifications shall include all revisions, changes,

and amendments.

Key personnel involved in the project and their quality control roles and responsibilities are

described below in Section 2.3.1 and Section 2.3.2. Since personnel assignments are subject to

change over time, the consultant’s resident engineer will maintain quality control staffing list

together with personnel assignments including the description of each position, along with

information on the responsible organization. When personnel changes occur, consultant’s

resident engineer will revise the quality control staffing list accordingly.

2.3.1 Consultant’s Quality Control Personnel

Concrete deals with testing materials and ensuring the properties meet specification

requirements. However, before concrete is placed, the specification requirements regarding

excavation, formwork, steel reinforcement, and construction joints must be inspected. Inspectors

must familiarize themselves with the specifications, including relevant drawings. Daily reports

should be prepared that document observations made during the inspection of the placement of

steel reinforcement and formwork. Required excavations should be verified by inspection and

testing, and appropriate reports prepared. Therefore consultant’s personnel should understand

and critically evaluate every single step in concrete construction.

The following key quality control personnel will be identified prior to the start of any concrete

construction works. A list of all quality control personnel will be provided to AAHDPO,

including the following details for each personnel: name, main responsibilities, qualifications

and years of work experience in the same field.

A. Consultant's Resident Engineer

The consultant’s resident engineer or representative is the primary point of contact for consultant

on all construction management issues. The resident engineer is responsible for the overall

management of activities related to the construction program, including the implementation of

the quality control plan and the health and safety program. As such, the resident engineer will



exercise approval authority over contractor submittals including the quality control plan. The

quality control plan shall include the names and qualifications of contractor’s quality control

personnel.

B. Consultant’s Site Monitoring Engineer/ Senior Construction Engineer

The consultant’s site monitoring Engineers manage the field implementation of the quality

control plan at the project sites under control of quality control manager. The consultant’s site

monitoring engineers will monitor the day-to-day activities of the contractor. This includes

ensuring that contractors comply with the plans and specifications, applicable building codes,

good workmanship, and the quality control requirements of the contract.

As part of this effort, the consultant’s site monitoring engineers will:

Conduct independent inspections to verify the quality of the work,

Participate in contractor three phase quality control inspections to enhance the level of

quality of concrete,

Review test and inspection reports as necessary and

Ensure that the required documentation for QMS is submitted.

The consultant’s site monitoring Engineers shall be alert of detecting, recording, and reporting

any deviation from the contract documents, including calling any deficient item to the attention

of the contractor’s superintendent, and to the resident engineer. The consultant’s site monitoring

engineers shall keep accurate and detailed records of the contractor’s performance and progress,

delivery of materials if any, and other pertinent matters, including the daily inspection report.

C. Consultant’s Quality Control Manager

The Consultant’s quality control manager is full-time consultant’s employee. The quality control

manager shall have a minimum of five years’ experience in related construction and prior quality

control experience on a project of comparable size and scope to this project.



Additional qualifications for the quality control manager include one or more of the following

requirements:

Two years of related quality control experience with a Bachelor of Science Degree in

Civil Engineering or Construction Technology and Management.

The quality control manager reports directly to the resident engineer. The quality control

manager will have full authority delegated by the consultant to institute actions necessary

for the successful implementation of the QC program to ensure compliance with the

contract plans and technical specifications (including stop-work authority). The quality

control manager should be assigned to the program full time.

The quality control manager works with consultant’s resident engineer to administer and

implement the quality control plan. This includes controlling this quality control plan,

making revisions as necessary, and implementing systematic actions to ensure

compliance with the plan. The quality control manager coordinates and oversees the

consultant’s construction engineers to ensure that inspection staff, third party inspection

and testing firms as well as contractor quality control staff carry out the requirements of

the concrete quality control plan.

The quality control manager tracks and reports non-conformances to the resident

engineer. The quality control manager also has full authority to obtain direct access to

contractor quality control files.

Other quality control manager responsibilities include;

Reviewing contractor quality control reports, tests, and inspection results,

Facilitating the implementation of the three-phase inspection program and participating in

the required inspections and

Ensuring that quality control personnel conducting inspections, including consultant’s

site monitoring engineers, are adequately trained and understand assignment limits and

time frames.



2.3.2 Contractor’s Quality Control Personnel

The following key quality control personnel will be identified prior to the start of any

construction works. A list of all quality control personnel will be provided to the consultant,

including the following details for each personnel: name, main responsibilities, qualifications

and years of work experience in the same field.

A. Contractor Quality Control Systems Manager

The contractor quality control systems manager is a full-time employee of the contractor, or a

consultant engaged by the contractor. The quality control systems manager shall have a

minimum of four years of experience in related construction, prior quality control experience on

a project of comparable size and scope to the contractor’s scope of work on this project and shall

have Bachelor of Science degree in Civil Engineering or Construction Technology and

Management. Contractor quality control staffs will be engineers or engineering technicians, and

will have a minimum of two years of experience in their area of expertise. Additional experience

and training may be substituted for educational requirements, subject to consultant’s/Engineer’s

approval.

The quality control systems manager will have full authority to institute any and all actions

necessary for the successful implementation of the quality control program to ensure compliance

with the contract plans and technical specifications. The quality control systems manager shall

report directly to a responsible project manager or officer of the construction contractor.

The contractor quality control systems manager and staff should perform the following

functions:

Inspect all materials, construction, and equipment for conformance with the technical

specifications,

Perform all quality control tests as required by the technical specifications,



SECTION 3

SUBMITTALS

This section describes the procedures for submittals. The consultant’s resident engineer shall

administer, control, and process submittals from the construction contractor(s). The consultant’s

resident engineer shall review all contractor submittals, and related supporting documents, to

ensure compliance with project specifications and drawings. The submittals disposition will be

noted on the submittal, which will be signed, dated and recorded. If required, consultant’s

resident engineer will return the submittal to the contractor for revision, incorporating the

comments. The contractor shall resubmit it for review and verification for compliance.

Submittals will be logged and copies will be retained in the project files.

3.1 Submittal Schedule

The construction contractor will prepare and submit a submittal schedule to the consultant’s

resident engineer. The schedule shall be initially submitted within 14 days after the award of the

contract and updated on a monthly basis. The resident engineer shall work with the contractor to

prioritize and sequence submittals so that the most critical submittals are received and processed

first. The submittal schedule will become the baseline against which receipt of all required

submittals will be compared.

The approved submittal schedule will be forwarded to Addis Ababa Housing Development

Project Office (AAHDPO) for resource allocation planning.

3.2 Process, Review and Acceptance

Submittals will be managed as follows:

1) Contractors will number and certify the completeness of all submittals before submitting

to consultant;

2) Contractors shall also complete submittal transmittal forms and submit four paper copies

and one electronic copy of all required submittals to the consultant’s resident engineer;



3) Upon receiving the submittal, the resident engineer will log the submittal and provide a

review to ascertain whether the package is complete. If the submittal is incomplete the

submittal will be returned to the contractor.

4) The original submittal transmittal and all copied attachments will be logged into the

document tracking system.

5) The resident engineer shall review the submittal for general conformance with contract

design documents, will coordinate concurrent discipline reviews within the design team,

quality control manager, and consolidate responses into a single coordinated action.

6) The consultant will return a copy of the submittal to the contractor with an original stamp

of the action required.

7) The six actions that may be taken for each submittal which are:

i. Approved – Submittal meets contract requirements. No additional copies will be

required of the contractor.

ii. Approved As Noted – Submittal meets contract requirements with minor corrections

noted. Re-submittal is not required. Contractor shall incorporate the required

corrections into the work in the field. No additional copies will be required of the

contractor.

iii. Revise and Resubmit – Submittal has some selected areas that do not meet

requirements. These areas can be revised to meet requirements, and the entire

submittal shall be re-submitted for review and approval. No work will begin in the

field until the revised submittal has been approved.

iv. Rejected – Submittal is inadequate and does not meet contract requirements. Revise

the complete submittal and resubmit for approval. No work will begin in the field

until the revised submittal has been approved.

v. For Information Only – Submitted for information only; no response action required.

vi. Received, No Action Taken – Receipt of submittal is noted; no further action

required.



8) When a submittal is to be revised and resubmitted, the contractor will revise the submittal

and indicate this revision by incrementing the revision number.

9) The resident engineer is responsible for tracking the submittal package during the entire

review process and advising all concerned of any schedule impacts to ensure that the

review process time frame is adhered to. The resident engineer will retain copies of all

submittal documents and revisions and ensure that an accurate file is available for ready

retrieval during the life of the project. The resident engineer will maintain all submittal

files. These files will be filed by numeric sequence. Each submittal file will contain a

complete submittal copy of the submittal before and after the review process.

3.3 Storage

The resident engineer will maintain all submittal files via a combination of a secure document

filing and storage system, and a computerized document tracking system. All submittal records

will be available for review by all stakeholders. All submittal records will be provided to Addis

Ababa Housing development project office (AAHDPO) as part of the project closeout

documentation.



SECTION 4

PERFORMANCE MONITORING REQUIREMENTS

The performance monitoring requirements are applicable to all projects under Addis Ababa

Housing Development Project Office. The contract technical specifications impose these

requirements upon the contractors and require specific plans for contractor compliance and

related work-area monitoring. The resident engineer will perform quality control oversight of

contractor compliance and related work-area monitoring pursuant to the submitted plans.

4.1 Environmental Protection Plan

Environmental Protection Plan (EPP) outlines the steps that contractor will follow to minimize

any adverse impact upon the environment in accordance with client requirements for the

implementation of this project to realizes that there are threats to the environment from the

project operations that must be eliminated or minimized. It is the contractor intention to spare no

effort to prevent environmental pollution during and as a result of construction operations under

this contract. Contractor should comply with all local, regional or Ethiopian government laws,

rules, regulations or standards concerning environmental pollution control and elsewhere in the

contract specifications.

Clauses should be written into the contract documents for the construction to ensure that the

contractor is aware of their responsibilities. A summary of contractual obligations imposed on

the contractor shall be presented in contract document, the contract clause ensure that the

contractor adopt appropriate practices with respect to the following:

Environmental protection,

Minimizing negative impacts on local communities, and,

Securing the health, safety and welfare of the workforce

Typically potential negative impacts associated with construction activities can be eliminated or

minimized by good engineering practices including consultation with affected parties and

thoughtful planning.



4.1.1 Contractor’s Responsibilities

The Contractor shall be responsible for implementing environmentally and socially sound

execution of the works (temporary and permanent) associated with the rehabilitation of the

horizontal and vertical structure projects.

In particular, when providing facilities and carrying out construction activities, the Contractor

must ensure the following:

Safeguard all workers from any hazards associated with the construction activities and

ensure protection of their health and safety.

Ensure protection of the health, safety and welfare of project side communities by

minimizing nuisance (including traffic disruption and pollution), friction and by

establishing effective channels of communications.

Observe the National Environmental Laws and other existing regulations of Ethiopia.

Liaise with statutory undertakers for smooth and efficient operation and completion of

projects.

4.1.2 Key Activities for Monitoring During Construction

The core issues that will be subject to environmental and social protection monitoring during

construction are as follows:

Effluent and solid waste disposal,

General road safety management particularly with respect to diversions, construction

through settlements, construction traffic and maintenance of existing road surfaces,

Health, safety and welfare of the workforce,

Community relations and mitigation of social tensions, and

Impact levels of nuisance such as dust and noise.

Monitoring for compliance shall be a day-to-day affair carried out by all client’s, consultant’s

and contractor’s concerned personnel and staff.



4.2 Reporting

The monitoring data obtained by the resident engineer during construction work will be included

in the weekly progress report.

4.2.1 Quality Control Report

A complete and accurate weekly report shall be prepared. The following information shall be

included:

1) Project conditions– weather, moisture, soil conditions, etc. A detailed note on when and

how adverse condition hampered or shut down a contractor’s operation shall be included.

2) Activities– work phases, including locations. Details on description of each activity and

the quality inspection phase, i.e., Preparatory, Initial, Follow-up, shall be included.

3) Controversial matters– disputes, questionable items, etc. A detailed note if such

disputes were settled and, if so, how they were settled.

4) Deficiencies and violations – description, location and corrective action taken on

observed deficiencies and violations.

5) Instructions given and received– identify recipient and source.

6) Progress information– report all delays, action taken or action contemplated.

7) Equipment – report arrival and departure of each major item of equipment by

manufacturer, model, serial number and capacity; also report equipment in use and idle

equipment.

8) Reports –make sure quality assurance reports are identified, dated and signed.

Check the quality control plan weekly report each week for accuracy and to assure that

instructions received are noted. Effectiveness of the quality control plan inspections reported

shall be checked during the job site visit.



4.2.2 Progress Schedules

1) Render any necessary assistance to the contractor for his/her preparation of initial and

revised progress schedules.

2) Encourage contractor to submit timely updates.

3) Be familiar with the approved progress schedule and carefully watch for any slippage in

progress.

4) Anticipate slowdowns and delays affecting progress.

5) Promptly report to the resident engineer and record in the daily quality control reports, all

indications of any slippage in progress.

6) When construction falls behind schedule, carefully examine the construction operations

for ways progress can be improved.

7) Be very careful not to direct or dictate the contractor’s operation, if needed, only the

quality control manager may want to direct the contractor to take steps to improve his

progress.

Keep informed of the required contract completion date and know the advance notice required by

higher authorities for pre-final and final inspections.



SECTION 5

INSPECTION AND VERIFICATION ACTIVITIES

The quality control, verification, and acceptance testing plans will set out the quality control

inspections and testing for implementation of technical specification applicable to the

contractor’s concrete related scope of work. The plans will cover the type, test standard,

frequency, control requirements, and assigned responsibility for inspections and tests. The

consultant’s resident engineer will review and approve these plans as part of the contractor

quality control plan submittals.

Ongoing quality control monitoring and oversight of contractor quality control inspections and

testing will be performed by the consultant’s resident engineer and other quality control staffs. In

this manner, the inspections and tests required to measure compliance with the relevant portions.

5.1 General Construction Inspection and Verification Requirements

Contractors shall perform the inspections and tests as prescribed in the technical specifications

for contracts. Quality control inspection and testing will be used to verify the adequacy and

effectiveness of the contractor concrete quality control program. The quality control inspection

and testing frequency will be at the discretion of the quality control manager based on results of

quality control tests, evaluation of daily reports, audits of the quality control program and

verification testing conducted by the consultant and the contractor’s in-house or third party

testing firm. Should information become available that indicates a potential problem, the quality

control manager will review in detail all pertinent information and order additional verification

testing if necessary. Contractor quality control, verification, and acceptance testing plans will set

out the contractor’s specific quality control testing and inspection. The different inspection forms

to be used for such purposes are attached in the appendix part of this document. The forms are

for illustration only and are not intended to replace or modify contract specifications that will

form the basis of actual quality control plan submittals.



5.1.1 Inspections

The contractor shall establish a program for inspection of activities affecting quality of the

concrete structures and shall cover all construction site and laboratory operations, including both

onsite and offsite operations. Inspections shall be performed to verify compliance with

documented instructions, drawings, procedures, and specifications as required by the contract.

All inspections shall be conducted and documented by the contractor and consultant as required

by technical specification. The checklists shown below will be used during inspection.

Checklists: Please see the attached sample checklist in appendices.

Quality Inspection Program: A four-phase inspection program shall be followed for

each concrete work.

The four phases of quality inspection are:

1. Preparatory Quality Inspection: The contractor and consultant perform preparatory

inspections prior to beginning any work on any definable feature of the concrete work.

a) Ensure that preparatory inspections include a review of contract requirements.

b) Ensure that all materials that uses for concrete production have been tested, submitted,

and approved based on contract document and respective standards.

c) Ensure that provisions have been made to provide required testing for intended quality.

d) Examine work area to ascertain that all preliminary work has been completed before

concrete production is taking place.

e) Examine materials, equipment, and samples to ensure that they conform to approved shop

drawings or submittal data, that all materials and/or equipment are on hand, and that all

monitoring and measuring equipment is properly calibrated and in proper working

condition.

f) Record preparatory inspections in the contractor’s quality control documentation as

required by technical specification.



2. Initial Quality Inspection: The contractor and consultants perform an initial inspection as

soon as a representative portion of the particular feature of work has been accomplished.

a) Examine the quality of workmanship.

b) Review control testing for compliance with contract requirements.

c) Review dimensional aspects of the work.

d) Record initial inspections in the contractor’s quality control documentation as required by

technical specification.

3. Follow-up Quality Inspection: The contractor and consultant perform follow-up inspections

daily.

a) Ensure continuing compliance with Contract requirements.

b) Ensure continuing compliance with control testing until completion of particular concrete

work.

c) Contractor quality control manager records follow-up inspection in daily quality control

reports.

d) Consultant’s quality control manager records follow-up inspections in their daily

inspection report.

e) Conduct final follow-up inspections and correct test deficiencies prior to the addition of

new feature of concrete work.

4. Completion Inspection: The contractor and consultant perform a completion inspection of

the work.

a) Develop a “punch list” of items that do not conform to the approved plans and

specifications.

b) Include the punch list in the construction quality control documentation as required by

technical specification. Include the estimated date by which the deficiencies will be

corrected.



c) Perform a second completion inspection after punch list items have been completed and

the resident engineer has been notified by the contractor.

Once all phases of inspection are completed it shall be included in the weekly inspection report.

The weekly inspection reports shall identify inspections conducted, results of inspections,

location and nature of defects found, causes for rejection, and remedial or corrective action taken

or proposed.

Additional quality control inspections may include inspection of third-party lab testing facilities,

and suppliers. Other inspections outside of the four-phase program described above will be

ordered or performed by the consultant to verify compliance with building code and standards.

These inspections shall be performed and conducted at various points of construction that would

typically require code compliance inspections. For code references Ethiopian Building Codes of

standard (EBCS-2), ACI 318 and other codes can be applied to verify compliance and

conformity to the contract specification and expected quality.

When deficiencies are discovered during the four-phase or other inspection processes, focused

inspection shall be considered by the quality control manager. When material or performed

work, is found on the basis of focused inspections to be deficient and/or does not meet the

project specifications, the quality control manager will assure deficiency correction is

implemented.

AAHDPO sub-branches project office shall be allowed to participate in any and all inspections in

necessary conditions to enhance the quality of concrete structures of the buildings and the office

shall also check and supervise whether consultants are working on inspections and quality

control to improve the quality of concrete produced of those projects.

5.1.2 Contractor Concrete Quality Control Testing

As required by the contract specifications, the contractor shall establish a test program to ensure

that all required testing is properly identified, planned, documented and performed under

controlled and suitable environmental conditions. Testing shall be performed in accordance with

written test procedures in the quality control plan.



Such test procedures shall incorporate or reference the requirements as contained in the contract

technical specifications, codes and industry standards. As per the quality control plan, the

contractor shall submit the test procedures to the quality control manager for review and

acceptance prior to their implementation.

The contractor shall propose a materials testing laboratory as part of the work plan. Consultant’s

approval of the proposed laboratory shall be provided in accordance with the following criteria:

Qualification of key personnel and laboratory technicians.

Calibration documentation for all testing equipment for required tests.

Availability, condition, and capacity of facilities and testing equipment.

The contractor shall be responsible for establishing a system of periodic test reports that will

record all quality control test results. Test results shall be submitted to the quality control

manager prior to the start of the next concrete work period. When required by the technical

specifications, the contractor shall maintain statistical quality control charts. The contractor’s

responsible technician shall sign the test reports. The quality control manager will review test

results and identify any non-conforming test results for discussion with the contractor regarding

potential corrective action.

5.1.3 Consultant’s Concrete Quality Control Testing

The consultant’s quality control manager will be responsible for the quality control of concrete

making materials and testing program. The consultant quality control testing is provided for the

verification of the adequacy and effectiveness of the contractor’s concrete quality control testing.

Quality control testing is assured by the quality control manager. QC testing may be performed

on a pre-established schedule or as directed by the quality control manager when it is necessary.

Quality control testing will be performed by or under supervision of the quality control staff to

validate the contractor’s quality control sampling and testing with acceptable standards. Such

testing may be performed by third party testing services.



The typical test frequency will be based on the decision by the consultant based on applicable

codes of standards for concrete quality testing and minimum test request on the contract

document.

More frequent testing during initial startup may be necessary to verify that concrete production is

under control and complies with the technical specifications of the construction contracts. In lieu

of performing independent tests the quality control manager may choose to witness quality

control testing or conduct tests on split samples from quality control testing. When concrete

quality control test results do not compare or have wide variances with the specification,

additional testing may be needed to validate the results. Additional tests to be performed by field

inspectors or the third party testing services will be at the direction of the quality control

manager. The need for quality control testing shall be based on the following considerations:

a) Importance of the item as to its reliability,

b) Need to perform quality checks for fabrication sequences not available for inspection at

completion, and

c) Deficiencies are discovered.

QC testing shall be performed in accordance with the following:

a) The quality control manager shall develop a weekly or per necessary structure quality test

and inspection schedule using the construction activity forecast as a guide. The schedule

shall: identify the quality assurance test activities and identify the hold points.

b) The weekly or per necessary structure quality test schedule shall be distributed to the

Engineer and Engineers field staff.

c) The contractor shall be provided a one-day advance notice of impending hold points.

Site monitoring engineers conducting the quality tests and inspections shall complete the daily

construction report included in appendixes. The daily construction report shall be distributed to

the quality control manager, resident engineer, monitoring engineer, contractor project manager

and/or quality control systems manager. The quality control manager will review quality control

tests and maintain files for all fields’ quality control documentation.



5.2 Concrete Construction Acceptance Criteria

Concrete construction acceptance criteria for materials qualifications, inspection, and testing are

established by technical specifications and code of standards. Ethiopian Building Code of

standard (EBCS-2), ACI 318 and other relevant code of standards give guidance on acceptance

criteria's for quality of concrete and its ingredients. This CQMP document illustrates concrete

quality control tables included in Appendices A (materials qualifications), B (inspection), and C

(testing). Criteria for concrete materials and equipment shall be set by and submitted to Addis

Ababa housing development project office in accordance with the applicable codes and standards

and by manufacturers’ recommendations. Contractor submittals are to document conformance

with acceptance criteria as detailed in their quality control plan (control, verification, and

acceptance testing plan).

5.3 Compliance with Handling, Storage, Packaging, Preservationand Delivery Requirements

Consultant’s field staffs will inspect the construction contractor’s activities to ensure technical

compliance in identification, handling, storage, packaging, preservation, and delivery of concrete

making materials (i.e. cement, fine and coarse aggregate, water and additives if any) and

production of quality concrete structures. Related quality records and documents will be

maintained and controlled in accordance with the procedures provided in Section 7 of this

concrete quality control plan document.

5.4 Material Identification and Traceability

Consultant’s field staffs will monitor the construction contractor to ensure that identification and

traceability requirements are met. Products and materials used in concrete production shall be

traced from receipt through all project stages to installation. Documentation such as project

control checklists, material receipts, material tracking forms, procedures, sample and test

documentation, and reports will ensure that the applicable material item traceability is

maintained.



Concrete production specifications and procedures shall define product identification and

traceability requirements, which generally include the following:

a) Concrete materials or equipment intended for use in concrete construction are identified

and segregated until inspection confirms that they conform to technical and quality

requirements, and

b) Concrete materials are traceable to documents attesting to their conformance with

technical requirements that are stated in specifications or drawings. Testing of concrete

materials will also be conducted as necessary to verify conformance with concrete

material specifications.



SECTION 6

CONSTRUCTION DEFICIENCIES

This section provides procedures for tracking concrete construction deficiencies (non-

compliance) from identification through acceptable corrective action. It defines the controls and

related responsibilities and authorities for dealing with non-compliant concrete products.

6.1 Deficiency Identification

Deficiency occurs when a concrete material or concrete production process of the performed

work does not meet the plans or specifications for the project. Therefore, to avoid such

deficiency, stakeholders should plan and collaborate in enhancing the quality of concrete. In this

project the major stakeholders that are responsible in enhancing the quality of concrete are, the

client (AAHDPO) who is the owner of the project, consultants who are hired by AAHDPO for

supervision and quality control and contractors who construct the project buildings.

6.2 Quality Control Deficiency Identification and Control ofconcrete

When concrete materials or concrete work is found deficient, the quality control manager shall

ensure that the non-conforming concrete material or concrete work is identified and controlled to

prevent unintended use or delivery. The consultant will notify the contractor of non-compliance

with any of the foregoing requirements. The contractor shall, after receipt of such notice,

immediately take corrective action.

Minor deficiencies noted during test or inspection are be verbally reported to the contractor’s

representative and noted on the weekly construction report. Minor deficiencies are items that do

not require significant rework or repair work to correct, and will not result in significant

deviations from required quality standard if corrected immediately.

Control and disposition of such deficiencies shall be by the originator of the weekly construction

report and the contractor’s supervisor responsible for the work and do not require formal action

by consultant. Ideally, such minor deficiencies can be corrected on the spot by agreement with

the contractor’s supervisor.



Non-conformances are major deviations from the contract requirement and/or accepted standard

of quality, which shall be formally documented for corrective action by consultant’s field staff or

the third party testing group. Failure by a contractor to correct a minor deficiency after having

been put on notice will also result in a non-conformance if it is not corrected within 5 days of

notification. The Non-Conformance Report (NCR) is a formal notification to the contractor that

work does not meet the plans or the specifications for the project. Any item of work found to be

deficient, out of conformance with the construction drawings and/or specifications will be

identified by the inspector on the nonconformance report as described in this section. Non-

conformance reports will be included on the non-conformance log and tracked through

verification that the non-conformance has been corrected.

Non conformances shall be formally documented on the NCR form and an example form is

shown in Appendix D. The Non-conformance report shall be distributed to the contractor quality

control manager, resident engineer, and AAHDPO sub branch office.

The consultant’s quality control manager shall follow up on the Non-conformance report as

required to verify that corrective action has been completed. The consultant shall verify and

accept the corrected work by actual inspection.

6.3 Quality Control Deficiency Correction

When concrete material, performed concrete work is found to be deficient and/or does not meet

the project specifications and standards, the quality control manager will assure and follow

deficiency correction is implemented.

The quality control manager shall ensure that the non-conforming concrete material or concrete

work is identified and controlled to prevent unintended use or delivery. The non-conforming

concrete materials shall be discarded from production site to preclude their unintended use and

concrete work shall be tagged by the construction contractor and consultant's staffs until

solutions are provided for compliance and acceptance. The quality control manager is

responsible for documenting the non-conformance in a NCR as specified in Section 6.2.

Contractors will implement corrective actions to remedy concrete work that is not in accordance

with the drawings and specifications. The corrective actions will include removal and



replacement of deficient concrete work using methods approved by the resident engineer.

Removal shall be done in a manner that does not disturb concrete work that meets quality control

criteria; otherwise, the disturbed concrete work shall also be rechecked by non destructive tests

after removal of deficient concrete work. In case of non compliance of the concrete work it

should be removed and replaced. Replacement shall be done in accordance with the

corresponding technical specifications. Replacement will be subjected to the same scope of

quality control inspection and testing as the original work. If the replacement work is not in

accordance with the drawings and specifications, the replacement work will be removed,

replaced, re inspected, and re-tested.

6.4 Preventive Actions

Preventive actions are to be taken to eliminate the cause of a potential non-conformity. For

example, defects that appear on concrete during construction or within a relatively short time

after completion are usually caused by poor quality materials, improper mix design, lack of

proper placing and curing procedures, or poor workmanship. Contractors shall take preventive

actions as necessary to eliminate the causes of potential deficiencies so as to prevent their

occurrence. Contractor’s concrete quality control plans are to include quality improvement

practices to continually improve construction practices and address quality problems at their

source. The resident engineer and quality control manager are to monitor, inspect, and audit

processes used to prevent erroneous information or construction products from being passed to

the owner.

The resident engineer and quality control manager have the authority to implement, verify and

review the project’s preventive and corrective action effectiveness. They are empowered to

improve the project’s work processes to eliminate the causes of potential non-conformities.

Contractor’s quality control documentation shall cover all aspects of quality control program

activities, and includes weekly inspection reports and test reports. After quality control plan

approval by the resident engineer, the contractors will document the quality control activities

pursuant to the quality control plan. Ongoing quality control oversight will also be documented

by the resident engineer.



SECTION 7

DOCUMENTATION7.1 Daily Record Keeping

Project documents will be managed through a combination of a secure document filing and

storage system and a computerized document tracking system. Sufficient records shall be

prepared and maintained as concrete work is performed to furnish documentary evidence of the

quality of concrete construction and laboratory analysis and activities affecting quality of

concrete. A consultant quality control manager shall maintain a daily log of all inspections

performed for both contractor and subcontractor operations.

The daily inspection and test reports shall be signed by quality control manager or delegated

authority. The resident engineer shall be provided at least one copy of each daily inspection and

test report on the work day following the day of record.

7.2 Daily Construction Report

A daily construction report will be prepared and signed by the resident engineer or delegated

authority. The report will include a summary of the contractor’s concrete construction activities

if any. Supporting inspection data sheets will be attached to the daily report where needed.

Example forms are provided in Appendix D.

At a minimum, the daily construction report will include the following information:

a) Date, project name, location, and other identification

b) Description of weather conditions, including temperature, cloud cover, and precipitation

c) Reports on any meetings held and their results

d) Record of visitors to site

e) Locations of concrete construction underway during that day

f) Equipment and personnel working in each activity, including subcontractors

g) Descriptions of work item being inspected



h) Decisions made regarding approval of concrete material or of concrete work, and

corrective actions to be taken

i) Description of problems or delays and resolution

j) Communications with contractor staff

k) Construction activities completed and/or in progress

l) Progress photos, where applicable

m) Signature of the report preparer

The daily construction reports will be routed on a daily basis to the project quality control files

and will be maintained as part of the permanent project record. These reports are reviewed by the

resident engineer and summarized in a weekly and monthly report, and also distributed to the

quality control manager.

7.3 Inspection and Testing Report Forms

Report forms will be completed for inspections and tests conducted. The forms vary depending

on inspection or test type. Representative forms for concrete construction inspection and testing

reports are included in Appendix D. These forms shall include:

a) Description or title of the inspection activity

b) Location of the inspection activity or location from which the sample was obtained

c) Recorded observation or test data

d) Results of the inspection activity

e) Personnel involved in the inspection activity

f) Signature of the inspector

7.4 Control of Concrete Quality Records

The quality control manager verifies concrete quality control record accuracy and maintains

copies of all quality-related documentation. This includes, but may not be limited to:

a) Concrete construction quality control logs and records;



b) Inspection checklists and reports;

c) Surveillance reports;

d) Non-conformance reports;

e) Material receiving reports; and

f) Monitoring and test data.

These records will be stored in files maintained in the project document control files.

The resident engineer has primary responsibility for the centralized document control files for

the project and construction documentation.

Pursuant to the contract specifications, the contractor provides an electronic or paper copy

(suitable for scanning) of quality control documentation associated with the work to document

control within three business days of the generation of such documents; and one electronic copy

of all required submittals to the resident engineer. The resident engineer shall maintain a fire-

resistant storage facility at the processing facility site. The facility shall contain all inspection

reports, test records, contract documents, project, and daily field reports.

All records shall be available for inspection and audit, at any time, by Addis Ababa housing

development project office.



SECTION 8

FIELD REVISIONS

Field revisions for concrete quality control will be limited to concrete quality control plan and

quality control plan changes. Changes to construction processes or design plans and

specifications are governed by the contract and design change order procedures.

8.1 Quality Control Plan Revisions

The resident engineer, site monitoring engineers, or quality control manager may initiate

revisions to this quality control plan. The CQCP may be revised when it becomes apparent that

the CQCP procedures or controls are inadequate to support concrete work being produced in

conformance with the specified quality requirements or are deemed to be more excessive than

required to support concrete work being produced in conformance with the specified quality

requirements. Changes to quality control procedures necessitating modification to this CQCP

will be initiated by the QCM for resident engineer's approval. AAHDPO review and approval

will then be accomplished. Updates to quality control plan staffing will be made by consultant

notification to AAHDPO sub-branch office without submission of a fully revised concrete

quality control plan (CQCP).

8.2 Contractors Quality Plan Revisions

The contractor’s quality control plans required by technical specification contractor quality

program requirements may require revisions as necessary to correct unsatisfactory performance.

At any time after approval by the resident engineer, the resident engineer may require the

contractor to make changes to the quality control plan, including personnel changes, as necessary

to obtain the quality specified. Moreover, the contractor may initiate quality control plan changes

to correct quality control process problems, and is required to notify the resident engineer in

writing of any desired changes; all changes are subject to project manager’s acceptance.

Revisions to the quality control plan will be provided to AAHDPO sub-branch office for

information only.



SECTION 9

FINAL REPORTING

The following quality related documents will be generated during implementation of all Addis

Ababa Housing development project office projects and will be submitted to AAHDPO.

9.1 Work Completion Report:

Once projects are completed all quality reports should be prepared and included with work

completion report. The report shall include record (as-built) drawings and operation and

maintenance manuals.



SECTION 10

REFERENCES

1. United Nations Office for Project Services (UNOPS), Construction Quality management

plan, www.unops.org.

2. CWN Project Management Limited, Quality Control plans Template, Harcourt Centre,

Block 4, Dublin, Ireland, www.cwnsas.com.

3. Construction Quality Control/Quality Assurance Plan, Phase 1 Facility Site Work

Construction, Hudson River Pubs Superfund Siege Company – Parsons Project Office

381 Broadway, Bldg 40-2, Fort Edward, NY 12828, 2007.

4. Quality Management Plan Guidance for Concrete used for Construction of Significant

Features, Technical Memorandum No. MERL-2015-073, U.S. Department of the Interior

Bureau of Reclamation Technical Service Center Denver, Colorado, 2015.



SECTION 11

APPENDICES



APPENDIX A

QUALIFICATION TEST SCHEDULES



Table -1: Qualification Test Schedule for Concrete Making Materials

Aggregate Materials (Fine and Coarse)

Test Parameter Test Method Minimum QCTesting Frequency

Requirements(verified by CQCM)

Standard Title

Coarse Aggregate

Grain-SizeDistribution

ASTMC136 /

-ES ISO6274:2014

Sieve Analysis ofFine and Coarse

Aggregates

At beginning ofplacing each mix.

At least every 400 m3

of placing a mix.

At change in mixdesign and materialsource.

CoarseAggregate meetssizing requirements as perASTM C33

-ES ISO 6274:2014

Moisture ContentASTM C566/

ES ISO6782:2014

Total EvaporableMoisture Content ofAggregate by drying



ofplacing a mix.

At change in mixdesign materialsource.

Verify that moisturecontent test is conductedwith accurate method andmaterialat batching site.Test method as per

-ES ISO 6782:2014

Fine Aggregate

Grain-SizeDistribution

ASTMC136 / ES ISO6274:2014

Sieve Analysis ofFine and Coarse

Aggregates 1 per stockpile andsource change

Fine Aggregate meets sizingrequirements as per ASTMC33/ ES ISO 6274:2014

Moisture Content

ASTM C566/ES ISO6782:2014

Total EvaporableMoisture Content ofAggregate by drying



ofplacing a mix.

At change in mixdesign materialsource.

Verify that moisture contenttest is conducted withaccurate method andmaterial at batching site.ES ISO 6782:2014

Note: This table is for illustration only and is not intended to replace or modify contract specificationsthat will form the basis of actual CQP submittals.



Table A-2

Cementations Materials (Cement)

Test Parameter Test MethodMinimum QC

Testing FrequencyRequirements

(verified by CQCM)

Portland Cement

Chemical and PhysicalRequirements

ASTM Cl50

Prior to use inconcrete mix inabsence of materialcertification.

In accordance with tables inASTM Cl50

andEthiopian Standard ES1177-

1:2005

Table A-3

Concrete Mix Field Tests

Minimum QC Requirements

Test Parameter Test Method Minimum QC Testing Frequency (verified by CQCM)

CompressiveStrength

ASTM C39/ES ISO1920-

4:2014

Preliminary testing of mix design; test at 28daysTake set of representative samples at leastfrom different structural members, i.e.,footing,columns,beams,slab, etc. and test7,14 and 28 days strength

İntended compressive strengthfor 28 days,EBCS- 2 compliance andconformity criteria

Water/CementRatio

ES ISO1920-2:2014

Preliminary testingof mix design

Limit to the intended mixdesign.

Slump TestASTM C143/ES ISO1920-

2:2014

Once per batch prior topouring concrete

Limit to the intended mixdesign.EBCS-2 also recommendsslump margins different mixes

Concrete Cores

ASTM C42/ES ISO1920-7:2014

At discretion of the consultant when cubestrengths fail to meet minimum requirements.

The contractor shall obtain core specimens orrebound hammer test in accordance withASTM C42 at locations directed by theconsultant. With no additional cost to theclient.

İntended compressive strengthfor 28 days

EBCS-2 also recommend thesetests.



APPENDIX B

INSPECTION SCHEDULE



TABLE B-1

AGGREGATE PLACEMENT / STORAGE

Inspection Parameter Minimum QC Acceptance Criteria

Inspection Frequency (verified by CQCM)

Coarse Aggregate

Material Characteristic Continuous As per standards and contract specifications

Maximum Size ContinuousIn accordance with the specification in thecontract document

Suitability of Placement DailyIn accordance with approved Work Plan.(Areas shall be free from organicimpurities)

Fine Aggregate

Material Characteristic ContinuousAs per standards and contractspecifications.

Maximum Size ContinuousIn accordance with the specification in thecontract document

Suitability of sandPlacement

DailyIn accordance with approved Work Plan.(Areas shall be free from organicimpurities)

Note: This table is for illustration only and is not intended to replace or modify contract

specifications that will form the basis of actual CQP submittals.



TABLE B-2

REINFORCING, FORMWORK AND CAST -IN -PLACE CONCRETE

Inspection ParameterMinimum QC

Inspection Frequency Acceptance Criteria (verified by CQCM)

Reinforcing MaterialCondition

Upon receipt at SiteNo visible defects or damage due tocorrosion, nounscheduled kinks or bends.

Reinforcing BundleIdentification

Upon receipt at Site

Bundled and tagged with enoughinformation that coonform withspecification

Reinforcing MaterialStorage

When necessaryIn accordance with Manufacturer'srecommendations and approved Work Plan

In-Place ReinforcingPrior to closing formsand continuous duringpouring

In accordance with approved Work Plan,free of old mortar, oils, mill scale andother encrustations or coatings

In-Place FormworkPrior to pouring ofconcrete

In accordance with approved Work Plan;no excess water, hardened concrete, debrisor foreign materials inside of forms, wetwood forms sufficiently to tighten upcracks

Concrete MixerBefore Concrete batching

is startedRPM of the mixer, Capacity to mix.

Surface PreparationPrior to pouring ofconcrete

Fine grade earth and aggregate smoothand level

Concrete PlacementContinuous duringPouring of concrete

In accordance with approved Work Plan,height of concrete drop not to exceed 1.5m,place and compact within 60 minutes afterwater is first added, do not place afterevidence of initial set

Formed Concrete CuringDaily during curing ofconcrete

Forms maintained in wet condition untilremoved, concrete continuously moist formin of 7 days after pouring

Formed ConcreteFinishing

After finishing ofconcrete

Fill holes and patch surfaces

Slabs and FlatworkCuring

Daily during curing ofconcrete

Concrete continuously wet for entirecuring period

Note: This table is for illustration only and is not intended to replace or modify contract

specifications that will form the basis of actual CQP submittals.



APPENDIX C

TEST SCHEDULES



Table c-1

TEST SCHEDULE FOR CONCRETE

Test Parameter Test MethodMinimum QC

Testing Frequency Acceptance Criteria

Compressive Strength

ASTM C39/ES ISO1920-

4:2014

1 per 38 m3 or fractionthereof from each day'splacing; test at 7, 14and 28 days

Intended compressivestrength of 28 days

EBCS -2 compliance criteria

Slump Test

ASTM C143/

ES ISO1920-2:2014

When compressiontest cubes are cast

In accordance with ASTMC143.



APPENDIX-D

TYPICAL CONCRETE CONSTRUCTIONFORMS



Concrete Compressive Strength Test Report form

(15x15x15cm-Cube )

( Astm C 39 )(Bs 1881)(Din 51220)

Date :Number:

Class of concrete : Crushing date of samples:

Slump: Temperature-

Description Age3 DaysIf Requıred

Age 7 Days Age 28 Days

Item

No.

Sample

Nu.

Place &Type Of

Structure

Weight(G)

StrengthWeight

(G)Strength

Weight(G)

Strength

KN Kg /Cm2 KN Kg/Cm2 KN Kg/Cm2

1

2

3

4

5

6

7

8

9

10

Specification :

Remarks:





CONCRETE INSPECTION AND TESTING PLAN

SUBJECT INS / TEST ACTIONQUALITY

CONTROL DOC.VERIFICATION

LOGREQ. OF

MONITORINGCOMMENTS

Controls before Concreting

1

REINFORCEMENT:Compliance withSpecs & Drwg., RustClearance – cleaningof elevation & axis

Site monitoringengineers / QualityManagers

DrawingsSpecifications

Reports, certificatesControl list beforeconcreting

2CONCRETEPremixed Concrete

Quality Control Specifications

Water, material,additive reportsConcrete mix &cement reports

3

FORMWORKElevation axes,Formwork Grease,Cleaning

Site monitoringengineers

ConstructionDrawingsSpecifications

Control list beforeconcreting

4

OTHERSLocation of embeddedelementsWater Retainers,Anchorage

Group EngineersConstructionDrawingsSpecifications

Control list beforeconcreting



Concreting

5

Taking ConcreteSamples, Slump,Cubes, Temperatureof the Medium,Concrete Temperature

Site monitoringengineers/ Qualitymanager

Test Results Recording

All the recording ofa conc.work is filedall together.(controllist conc, air temp.cube resistanceresults etc.)

6Concreting LocationControls


A Nonconformancereportis issued if needed.

The group eng.should be present tosee to itthatconcretingcomplies

7Compacting Control


A nonconformancereport isissued if needed.

The group engshouldattend Compacting

After Concreting

8 Controlling CuringSite monitoringengineers/ Qualitymanager

A nonconformancereport isissued if needed.

9Fault Areas andFixing

Site monitoringengineers

A non conformancereport isissued if needed.

Should containcorrective actionssuggested tocorrect andinformation statingthat these actionsare finalizedasrequired.

Segragation, airparticlesopening theformwork etc.



PRE-CONCRETING INSPECTION FORM

Explanation : Related Drawings :

Formwork Check Reinforcement Check Surveying Check Mechanical CheckElectrical and SanitaryCheck if Any

Supports Size Lining Embedments Embedments

Ties Spacing Level Blockouts Blockouts

Waterstops Laps Position Notes Notes

Joint Prepare Concrete Cover Sketch

Cleanliness Cleanliness

Formoil Quantity

Embedments

Blockouts

Contractor Contractor Contractor Contractor Contractor

Responsible Engineer

Name

Date

Signature


Name

Date

Signature


Name

Date

Signature


Name

Date

Signature


Name

Date

Signature



Permission Given to Pour

Consultant’s Representative

Name :

Date :

Sign :

Date of Concreting Type of Concrete Slump Site Manager

Notes :

Controls after formworkstriking

Curing

Line

Level

Position

Repairs

Consultant’s Representative Quality Control Manager

Name :

Date :

Sign :

Name :

Date :

Sign :



NON CONFORMITY REPORT FORM

Nonconformity Report Date:

Project

Related Section

Subject

Summary of Non-conformity

Prepared By Department

Summary of Disposition Plan

Approved By Department Date

Result Use - As – It - Is

Repair

Reject

Accepted

Rejected



CORRECTIVE ACTION COMPLETED FORM

Department Quality Control Manager

Name

Date

Signature

NON-CONFORMITIES LOG

NCR Record No NCR Date Brief Summary of Non-conformance

DispositionDate

Close-Out date

Documents

Advisor: Dr. Abraham Assefa Prepared By: Habtamu Sisay